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	$197.81	9.520%	$216.6415	$216.64	$216.65	$216.60
Purchase #2	$196.25	8.291%	$212.5211	$212.52	$212.50	$212.50
Purchase #3	$90.97	4.761%	$95.3011	$95.30	$95.30	$95.30
Purchase #4	$38.26	12.682%	$43.1121	$43.11	$43.10	$43.10
Purchase #5	$134.54	11.161%	$149.556	$149.56	$149.55	$149.60
Purchase #6	$236.56	7.181%	$253.5474	$253.55	$253.55	$253.50
Purchase #7	$31.55	4.271%	$32.8975	$32.90	$32.90	$32.90
7 purchase totals =	$925.94		$1,003.5767	$1,003.58	$1,003.55	$1,003.50