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	$153.83	10.643%	$170.2021	$170.20	$170.20	$170.20
Purchase #2	$165.51	7.708%	$178.2675	$178.27	$178.25	$178.30
Purchase #3	$78.79	12.721%	$88.8129	$88.81	$88.80	$88.80
Purchase #4	$28.57	12.703%	$32.1992	$32.20	$32.20	$32.20
Purchase #5	$87.67	5.725%	$92.6891	$92.69	$92.70	$92.70
Purchase #6	$148.75	3.185%	$153.4877	$153.49	$153.50	$153.50
Purchase #7	$98.54	13.166%	$111.5138	$111.51	$111.50	$111.50
7 purchase totals =	$761.66		$827.1723	$827.17	$827.15	$827.20