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	$101.27	10.415%	$111.8173	$111.82	$111.80	$111.80
Purchase #2	$27.89	5.763%	$29.4973	$29.50	$29.50	$29.50
Purchase #3	$243.29	13.307%	$275.6646	$275.66	$275.65	$275.70
Purchase #4	$226.51	10.190%	$249.5914	$249.59	$249.60	$249.60
Purchase #5	$160.39	13.823%	$182.5607	$182.56	$182.55	$182.60
Purchase #6	$204.59	13.133%	$231.4588	$231.46	$231.45	$231.50
Purchase #7	$153.86	8.795%	$167.392	$167.39	$167.40	$167.40
7 purchase totals =	$1,117.80		$1,247.9821	$1,247.98	$1,247.95	$1,248.10