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	$161.34	13.560%	$183.2177	$183.22	$183.20	$183.20
Purchase #2	$100.32	11.523%	$111.8799	$111.88	$111.90	$111.90
Purchase #3	$172.98	6.728%	$184.6181	$184.62	$184.60	$184.60
Purchase #4	$89.32	4.302%	$93.1625	$93.16	$93.15	$93.20
Purchase #5	$202.42	7.672%	$217.9497	$217.95	$217.95	$217.90
Purchase #6	$169.92	11.761%	$189.9043	$189.90	$189.90	$189.90
Purchase #7	$86.33	7.309%	$92.6399	$92.64	$92.65	$92.60
7 purchase totals =	$982.63		$1,073.3721	$1,073.37	$1,073.35	$1,073.30