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	$236.61	3.465%	$244.8085	$244.81	$244.80	$244.80
Purchase #2	$53.63	11.387%	$59.7368	$59.74	$59.75	$59.70
Purchase #3	$37.90	12.507%	$42.6402	$42.64	$42.65	$42.60
Purchase #4	$244.43	13.304%	$276.949	$276.95	$276.95	$276.90
Purchase #5	$31.84	12.627%	$35.8604	$35.86	$35.85	$35.90
Purchase #6	$197.28	5.848%	$208.8169	$208.82	$208.80	$208.80
Purchase #7	$31.52	4.364%	$32.8955	$32.90	$32.90	$32.90
7 purchase totals =	$833.21		$901.7073	$901.72	$901.70	$901.60