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	$42.35	7.318%	$45.4492	$45.45	$45.45	$45.40
Purchase #2	$100.96	12.819%	$113.9021	$113.90	$113.90	$113.90
Purchase #3	$227.65	3.360%	$235.299	$235.30	$235.30	$235.30
Purchase #4	$137.32	6.537%	$146.2966	$146.30	$146.30	$146.30
Purchase #5	$148.59	7.363%	$159.5307	$159.53	$159.55	$159.50
Purchase #6	$43.57	5.244%	$45.8548	$45.85	$45.85	$45.90
Purchase #7	$161.68	11.126%	$179.6685	$179.67	$179.65	$179.70
7 purchase totals =	$862.12		$926.0009	$926.00	$926.00	$926.00