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	$188.47	9.642%	$206.6423	$206.64	$206.65	$206.60
Purchase #2	$42.56	6.222%	$45.2081	$45.21	$45.20	$45.20
Purchase #3	$85.42	3.741%	$88.6156	$88.62	$88.60	$88.60
Purchase #4	$227.48	8.468%	$246.743	$246.74	$246.75	$246.70
Purchase #5	$64.30	11.752%	$71.8565	$71.86	$71.85	$71.90
Purchase #6	$223.35	12.307%	$250.8377	$250.84	$250.85	$250.80
Purchase #7	$165.85	13.678%	$188.535	$188.54	$188.55	$188.50
7 purchase totals =	$997.43		$1,098.4382	$1,098.45	$1,098.45	$1,098.30