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	$130.89	13.436%	$148.4764	$148.48	$148.50	$148.50
Purchase #2	$53.52	5.553%	$56.492	$56.49	$56.50	$56.50
Purchase #3	$146.40	6.498%	$155.9131	$155.91	$155.90	$155.90
Purchase #4	$231.45	5.158%	$243.3882	$243.39	$243.40	$243.40
Purchase #5	$225.43	11.571%	$251.5145	$251.51	$251.50	$251.50
Purchase #6	$155.59	3.185%	$160.5455	$160.55	$160.55	$160.50
Purchase #7	$17.50	4.495%	$18.2866	$18.29	$18.30	$18.30
7 purchase totals =	$960.78		$1,034.6163	$1,034.62	$1,034.65	$1,034.60