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	$131.25	8.200%	$142.0125	$142.01	$142.00	$142.00
Purchase #2	$86.57	4.170%	$90.18	$90.18	$90.20	$90.20
Purchase #3	$148.59	8.637%	$161.4237	$161.42	$161.40	$161.40
Purchase #4	$232.34	13.841%	$264.4982	$264.50	$264.50	$264.50
Purchase #5	$74.89	3.129%	$77.2333	$77.23	$77.25	$77.20
Purchase #6	$171.54	13.579%	$194.8334	$194.83	$194.85	$194.80
Purchase #7	$84.42	3.601%	$87.46	$87.46	$87.45	$87.50
7 purchase totals =	$929.60		$1,017.6411	$1,017.63	$1,017.65	$1,017.60