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	$31.69	5.584%	$33.4596	$33.46	$33.45	$33.50
Purchase #2	$79.87	4.496%	$83.461	$83.46	$83.45	$83.50
Purchase #3	$202.70	7.854%	$218.6201	$218.62	$218.60	$218.60
Purchase #4	$88.43	8.144%	$95.6317	$95.63	$95.65	$95.60
Purchase #5	$111.71	10.527%	$123.4697	$123.47	$123.45	$123.50
Purchase #6	$248.43	6.346%	$264.1954	$264.20	$264.20	$264.20
Purchase #7	$151.74	4.195%	$158.1055	$158.11	$158.10	$158.10
7 purchase totals =	$914.57		$976.9430	$976.95	$976.90	$977.00