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	$242.52	9.321%	$265.1253	$265.13	$265.15	$265.10
Purchase #2	$70.42	13.230%	$79.7366	$79.74	$79.75	$79.70
Purchase #3	$19.80	3.234%	$20.4403	$20.44	$20.45	$20.40
Purchase #4	$235.73	8.420%	$255.5785	$255.58	$255.60	$255.60
Purchase #5	$64.45	9.563%	$70.6134	$70.61	$70.60	$70.60
Purchase #6	$179.69	9.168%	$196.164	$196.16	$196.15	$196.20
Purchase #7	$243.34	8.123%	$263.1065	$263.11	$263.10	$263.10
7 purchase totals =	$1,055.95		$1,150.7646	$1,150.77	$1,150.80	$1,150.70