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	$64.63	10.785%	$71.6003	$71.60	$71.60	$71.60
Purchase #2	$148.72	6.839%	$158.891	$158.89	$158.90	$158.90
Purchase #3	$220.92	11.428%	$246.1667	$246.17	$246.15	$246.20
Purchase #4	$214.80	3.612%	$222.5586	$222.56	$222.55	$222.60
Purchase #5	$110.39	5.692%	$116.6734	$116.67	$116.65	$116.70
Purchase #6	$111.27	5.118%	$116.9648	$116.96	$116.95	$117.00
Purchase #7	$66.97	3.562%	$69.3555	$69.36	$69.35	$69.40
7 purchase totals =	$937.70		$1,002.2103	$1,002.21	$1,002.15	$1,002.40