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	$29.56	13.552%	$33.566	$33.57	$33.55	$33.60
Purchase #2	$146.98	12.853%	$165.8713	$165.87	$165.85	$165.90
Purchase #3	$159.37	5.598%	$168.2915	$168.29	$168.30	$168.30
Purchase #4	$190.45	5.788%	$201.4732	$201.47	$201.45	$201.50
Purchase #5	$51.79	9.790%	$56.8602	$56.86	$56.85	$56.90
Purchase #6	$221.48	4.823%	$232.162	$232.16	$232.15	$232.20
Purchase #7	$141.44	12.781%	$159.5174	$159.52	$159.50	$159.50
7 purchase totals =	$941.07		$1,017.7416	$1,017.74	$1,017.65	$1,017.90