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	$240.59	7.625%	$258.935	$258.94	$258.95	$258.90
Purchase #2	$243.43	4.120%	$253.4593	$253.46	$253.45	$253.50
Purchase #3	$195.50	6.849%	$208.8898	$208.89	$208.90	$208.90
Purchase #4	$48.73	12.190%	$54.6702	$54.67	$54.65	$54.70
Purchase #5	$101.73	6.673%	$108.5184	$108.52	$108.50	$108.50
Purchase #6	$130.44	8.494%	$141.5196	$141.52	$141.50	$141.50
Purchase #7	$65.72	11.380%	$73.1989	$73.20	$73.20	$73.20
7 purchase totals =	$1,026.14		$1,099.1912	$1,099.20	$1,099.15	$1,099.20