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	$65.52	9.575%	$71.7935	$71.79	$71.80	$71.80
Purchase #2	$76.73	6.807%	$81.953	$81.95	$81.95	$82.00
Purchase #3	$158.72	13.854%	$180.7091	$180.71	$180.70	$180.70
Purchase #4	$127.72	12.666%	$143.897	$143.90	$143.90	$143.90
Purchase #5	$211.35	10.255%	$233.0239	$233.02	$233.00	$233.00
Purchase #6	$113.59	3.176%	$117.1976	$117.20	$117.20	$117.20
Purchase #7	$147.90	11.854%	$165.4321	$165.43	$165.45	$165.40
7 purchase totals =	$901.53		$994.0062	$994.00	$994.00	$994.00