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	$229.94	7.388%	$246.928	$246.93	$246.95	$246.90
Purchase #2	$25.96	11.555%	$28.9597	$28.96	$28.95	$29.00
Purchase #3	$94.74	11.538%	$105.6711	$105.67	$105.65	$105.70
Purchase #4	$166.59	11.503%	$185.7528	$185.75	$185.75	$185.80
Purchase #5	$79.71	13.496%	$90.4677	$90.47	$90.45	$90.50
Purchase #6	$139.44	11.547%	$155.5411	$155.54	$155.55	$155.50
Purchase #7	$9.70	10.262%	$10.6954	$10.70	$10.70	$10.70
7 purchase totals =	$746.08		$824.0158	$824.02	$824.00	$824.10