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	$58.62	5.375%	$61.7708	$61.77	$61.75	$61.80
Purchase #2	$85.52	5.760%	$90.446	$90.45	$90.45	$90.40
Purchase #3	$38.38	7.590%	$41.293	$41.29	$41.30	$41.30
Purchase #4	$175.65	7.379%	$188.6112	$188.61	$188.60	$188.60
Purchase #5	$56.57	10.717%	$62.6326	$62.63	$62.65	$62.60
Purchase #6	$58.67	5.396%	$61.8358	$61.84	$61.85	$61.80
Purchase #7	$159.76	8.221%	$172.8939	$172.89	$172.90	$172.90
7 purchase totals =	$633.17		$679.4833	$679.48	$679.50	$679.40