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	$152.40	13.290%	$172.654	$172.65	$172.65	$172.70
Purchase #2	$181.74	4.389%	$189.7166	$189.72	$189.70	$189.70
Purchase #3	$100.59	7.576%	$108.2107	$108.21	$108.20	$108.20
Purchase #4	$141.84	9.497%	$155.3105	$155.31	$155.30	$155.30
Purchase #5	$213.69	6.490%	$227.5585	$227.56	$227.55	$227.60
Purchase #6	$95.61	10.690%	$105.8307	$105.83	$105.85	$105.80
Purchase #7	$181.57	7.869%	$195.8577	$195.86	$195.85	$195.90
7 purchase totals =	$1,067.44		$1,155.1387	$1,155.14	$1,155.10	$1,155.20