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	$131.74	12.444%	$148.1337	$148.13	$148.15	$148.10
Purchase #2	$169.86	3.215%	$175.321	$175.32	$175.30	$175.30
Purchase #3	$21.92	9.818%	$24.0721	$24.07	$24.05	$24.10
Purchase #4	$188.66	4.112%	$196.4177	$196.42	$196.40	$196.40
Purchase #5	$156.49	5.629%	$165.2988	$165.30	$165.30	$165.30
Purchase #6	$200.67	6.699%	$214.1129	$214.11	$214.10	$214.10
Purchase #7	$47.64	5.433%	$50.2283	$50.23	$50.25	$50.20
7 purchase totals =	$916.98		$973.5845	$973.58	$973.55	$973.50