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	$31.45	7.470%	$33.7993	$33.80	$33.80	$33.80
Purchase #2	$214.53	9.430%	$234.7602	$234.76	$234.75	$234.80
Purchase #3	$213.55	9.252%	$233.3076	$233.31	$233.30	$233.30
Purchase #4	$152.78	8.299%	$165.4592	$165.46	$165.45	$165.50
Purchase #5	$168.75	11.484%	$188.1293	$188.13	$188.15	$188.10
Purchase #6	$171.37	11.321%	$190.7708	$190.77	$190.75	$190.80
Purchase #7	$86.47	8.309%	$93.6548	$93.65	$93.65	$93.70
7 purchase totals =	$1,038.90		$1,139.8812	$1,139.88	$1,139.85	$1,140.00