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	$95.50	11.698%	$106.6716	$106.67	$106.65	$106.70
Purchase #2	$111.89	13.702%	$127.2212	$127.22	$127.20	$127.20
Purchase #3	$56.72	3.610%	$58.7676	$58.77	$58.75	$58.80
Purchase #4	$166.30	6.223%	$176.6488	$176.65	$176.65	$176.60
Purchase #5	$80.49	10.859%	$89.2304	$89.23	$89.25	$89.20
Purchase #6	$94.77	3.778%	$98.3504	$98.35	$98.35	$98.40
Purchase #7	$221.27	10.309%	$244.0807	$244.08	$244.10	$244.10
7 purchase totals =	$826.94		$900.9707	$900.97	$900.95	$901.00