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	$41.61	12.389%	$46.7651	$46.77	$46.75	$46.80
Purchase #2	$122.69	6.484%	$130.6452	$130.65	$130.65	$130.60
Purchase #3	$87.76	13.309%	$99.44	$99.44	$99.45	$99.40
Purchase #4	$95.59	10.520%	$105.6461	$105.65	$105.65	$105.60
Purchase #5	$82.83	9.746%	$90.9026	$90.90	$90.90	$90.90
Purchase #6	$196.55	3.372%	$203.1777	$203.18	$203.20	$203.20
Purchase #7	$247.45	11.205%	$275.1768	$275.18	$275.20	$275.20
7 purchase totals =	$874.48		$951.7535	$951.77	$951.80	$951.70