Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$158.43	8.830%	$172.4194	$172.42	$172.40	$172.40
Purchase #2	$123.57	7.549%	$132.8983	$132.90	$132.90	$132.90
Purchase #3	$59.80	5.139%	$62.8731	$62.87	$62.85	$62.90
Purchase #4	$185.96	7.320%	$199.5723	$199.57	$199.55	$199.60
Purchase #5	$158.51	12.654%	$178.5679	$178.57	$178.55	$178.60
Purchase #6	$232.68	3.524%	$240.8796	$240.88	$240.90	$240.90
Purchase #7	$90.58	3.587%	$93.8291	$93.83	$93.85	$93.80
7 purchase totals =	$1,009.53		$1,081.0397	$1,081.04	$1,081.00	$1,081.10