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	$91.30	8.793%	$99.328	$99.33	$99.35	$99.30
Purchase #2	$58.55	7.770%	$63.0993	$63.10	$63.10	$63.10
Purchase #3	$22.75	5.590%	$24.0217	$24.02	$24.00	$24.00
Purchase #4	$227.50	6.864%	$243.1156	$243.12	$243.10	$243.10
Purchase #5	$37.47	9.131%	$40.8914	$40.89	$40.90	$40.90
Purchase #6	$222.64	11.311%	$247.8228	$247.82	$247.80	$247.80
Purchase #7	$224.54	8.605%	$243.8617	$243.86	$243.85	$243.90
7 purchase totals =	$884.75		$962.1405	$962.14	$962.10	$962.10