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	$188.41	8.286%	$204.0217	$204.02	$204.00	$204.00
Purchase #2	$103.73	7.317%	$111.3199	$111.32	$111.30	$111.30
Purchase #3	$153.71	9.162%	$167.7929	$167.79	$167.80	$167.80
Purchase #4	$40.45	13.589%	$45.9468	$45.95	$45.95	$45.90
Purchase #5	$180.41	10.562%	$199.4649	$199.46	$199.45	$199.50
Purchase #6	$152.36	8.523%	$165.3456	$165.35	$165.35	$165.30
Purchase #7	$172.81	10.680%	$191.2661	$191.27	$191.25	$191.30
7 purchase totals =	$991.88		$1,085.1579	$1,085.16	$1,085.10	$1,085.10