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	$181.83	7.319%	$195.1381	$195.14	$195.15	$195.10
Purchase #2	$165.63	6.430%	$176.28	$176.28	$176.30	$176.30
Purchase #3	$177.95	10.659%	$196.9177	$196.92	$196.90	$196.90
Purchase #4	$146.55	12.829%	$165.3509	$165.35	$165.35	$165.40
Purchase #5	$41.40	10.129%	$45.5934	$45.59	$45.60	$45.60
Purchase #6	$92.31	8.409%	$100.0723	$100.07	$100.05	$100.10
Purchase #7	$236.75	5.686%	$250.2116	$250.21	$250.20	$250.20
7 purchase totals =	$1,042.42		$1,129.5640	$1,129.56	$1,129.55	$1,129.60