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	$47.72	10.239%	$52.6061	$52.61	$52.60	$52.60
Purchase #2	$171.85	7.131%	$184.1046	$184.10	$184.10	$184.10
Purchase #3	$110.53	7.534%	$118.8573	$118.86	$118.85	$118.90
Purchase #4	$111.50	12.846%	$125.8233	$125.82	$125.80	$125.80
Purchase #5	$149.57	10.502%	$165.2778	$165.28	$165.30	$165.30
Purchase #6	$172.33	13.522%	$195.6325	$195.63	$195.65	$195.60
Purchase #7	$227.93	13.439%	$258.5615	$258.56	$258.55	$258.60
7 purchase totals =	$991.43		$1,100.8631	$1,100.86	$1,100.85	$1,100.90