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	$186.34	13.281%	$211.0878	$211.09	$211.10	$211.10
Purchase #2	$146.88	9.795%	$161.2669	$161.27	$161.25	$161.30
Purchase #3	$76.78	11.830%	$85.8631	$85.86	$85.85	$85.90
Purchase #4	$123.77	10.157%	$136.3413	$136.34	$136.35	$136.30
Purchase #5	$47.82	3.655%	$49.5678	$49.57	$49.55	$49.60
Purchase #6	$246.86	13.110%	$279.2233	$279.22	$279.20	$279.20
Purchase #7	$178.73	5.225%	$188.0686	$188.07	$188.05	$188.10
7 purchase totals =	$1,007.18		$1,111.4188	$1,111.42	$1,111.35	$1,111.50