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	$198.37	12.391%	$222.95	$222.95	$222.95	$223.00
Purchase #2	$32.55	3.426%	$33.6652	$33.67	$33.65	$33.70
Purchase #3	$158.52	4.479%	$165.6201	$165.62	$165.60	$165.60
Purchase #4	$227.28	6.545%	$242.1555	$242.16	$242.15	$242.20
Purchase #5	$242.54	11.266%	$269.8646	$269.86	$269.85	$269.90
Purchase #6	$211.27	12.455%	$237.5837	$237.58	$237.60	$237.60
Purchase #7	$222.90	11.488%	$248.5068	$248.51	$248.50	$248.50
7 purchase totals =	$1,293.43		$1,420.3459	$1,420.35	$1,420.30	$1,420.50