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	$243.78	4.476%	$254.6916	$254.69	$254.70	$254.70
Purchase #2	$11.42	10.381%	$12.6055	$12.61	$12.60	$12.60
Purchase #3	$16.65	7.113%	$17.8343	$17.83	$17.85	$17.80
Purchase #4	$113.52	11.814%	$126.9313	$126.93	$126.95	$126.90
Purchase #5	$92.50	8.690%	$100.5383	$100.54	$100.55	$100.50
Purchase #6	$147.57	3.500%	$152.735	$152.74	$152.75	$152.70
Purchase #7	$220.43	8.111%	$238.3091	$238.31	$238.30	$238.30
7 purchase totals =	$845.87		$903.6451	$903.65	$903.70	$903.50