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	$61.37	4.518%	$64.1427	$64.14	$64.15	$64.10
Purchase #2	$64.56	13.775%	$73.4531	$73.45	$73.45	$73.50
Purchase #3	$193.95	13.693%	$220.5076	$220.51	$220.50	$220.50
Purchase #4	$6.59	10.777%	$7.3002	$7.30	$7.30	$7.30
Purchase #5	$55.26	11.675%	$61.7116	$61.71	$61.70	$61.70
Purchase #6	$70.62	10.857%	$78.2872	$78.29	$78.30	$78.30
Purchase #7	$209.27	11.339%	$232.9991	$233.00	$233.00	$233.00
7 purchase totals =	$661.62		$738.4015	$738.40	$738.40	$738.40