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	$82.99	4.665%	$86.8615	$86.86	$86.85	$86.90
Purchase #2	$154.46	11.600%	$172.3774	$172.38	$172.40	$172.40
Purchase #3	$8.59	3.427%	$8.8844	$8.88	$8.90	$8.90
Purchase #4	$9.76	4.515%	$10.2007	$10.20	$10.20	$10.20
Purchase #5	$9.37	13.682%	$10.652	$10.65	$10.65	$10.70
Purchase #6	$92.37	10.149%	$101.7446	$101.74	$101.75	$101.70
Purchase #7	$130.32	8.539%	$141.448	$141.45	$141.45	$141.40
7 purchase totals =	$487.86		$532.1686	$532.16	$532.20	$532.20