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	$123.66	5.744%	$130.763	$130.76	$130.75	$130.80
Purchase #2	$157.91	4.672%	$165.2876	$165.29	$165.30	$165.30
Purchase #3	$52.59	10.533%	$58.1293	$58.13	$58.15	$58.10
Purchase #4	$79.67	11.113%	$88.5237	$88.52	$88.50	$88.50
Purchase #5	$82.55	7.257%	$88.5407	$88.54	$88.55	$88.50
Purchase #6	$228.42	5.871%	$241.8305	$241.83	$241.85	$241.80
Purchase #7	$95.69	3.322%	$98.8688	$98.87	$98.85	$98.90
7 purchase totals =	$820.49		$871.9436	$871.94	$871.95	$871.90