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	$10.58	4.480%	$11.054	$11.05	$11.05	$11.10
Purchase #2	$233.83	8.248%	$253.1163	$253.12	$253.10	$253.10
Purchase #3	$130.33	10.772%	$144.3691	$144.37	$144.35	$144.40
Purchase #4	$37.63	7.540%	$40.4673	$40.47	$40.45	$40.50
Purchase #5	$36.48	3.708%	$37.8327	$37.83	$37.85	$37.80
Purchase #6	$98.93	5.802%	$104.6699	$104.67	$104.65	$104.70
Purchase #7	$219.68	12.852%	$247.9133	$247.91	$247.90	$247.90
7 purchase totals =	$767.46		$839.4226	$839.42	$839.35	$839.50