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	$92.85	8.223%	$100.4851	$100.49	$100.50	$100.50
Purchase #2	$232.46	8.205%	$251.5333	$251.53	$251.55	$251.50
Purchase #3	$35.34	8.210%	$38.2414	$38.24	$38.25	$38.20
Purchase #4	$68.57	13.612%	$77.9037	$77.90	$77.90	$77.90
Purchase #5	$167.72	7.594%	$180.4567	$180.46	$180.45	$180.50
Purchase #6	$239.43	6.252%	$254.3992	$254.40	$254.40	$254.40
Purchase #7	$140.58	12.612%	$158.3099	$158.31	$158.30	$158.30
7 purchase totals =	$976.95		$1,061.3293	$1,061.33	$1,061.35	$1,061.30