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	$130.29	9.716%	$142.949	$142.95	$142.95	$142.90
Purchase #2	$179.80	7.179%	$192.7078	$192.71	$192.70	$192.70
Purchase #3	$17.26	10.831%	$19.1294	$19.13	$19.15	$19.10
Purchase #4	$54.28	5.548%	$57.2915	$57.29	$57.30	$57.30
Purchase #5	$42.35	7.345%	$45.4606	$45.46	$45.45	$45.50
Purchase #6	$110.34	9.196%	$120.4869	$120.49	$120.50	$120.50
Purchase #7	$79.65	3.281%	$82.2633	$82.26	$82.25	$82.30
7 purchase totals =	$613.97		$660.2885	$660.29	$660.30	$660.30