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	$142.25	6.256%	$151.1492	$151.15	$151.15	$151.10
Purchase #2	$125.83	4.463%	$131.4458	$131.45	$131.45	$131.40
Purchase #3	$146.38	10.418%	$161.6299	$161.63	$161.65	$161.60
Purchase #4	$173.93	6.141%	$184.611	$184.61	$184.60	$184.60
Purchase #5	$143.42	9.265%	$156.7079	$156.71	$156.70	$156.70
Purchase #6	$88.28	12.600%	$99.4033	$99.40	$99.40	$99.40
Purchase #7	$244.66	5.855%	$258.9848	$258.98	$259.00	$259.00
7 purchase totals =	$1,064.75		$1,143.9319	$1,143.93	$1,143.95	$1,143.80