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	$233.43	9.467%	$255.5288	$255.53	$255.55	$255.50
Purchase #2	$116.57	12.589%	$131.245	$131.25	$131.25	$131.20
Purchase #3	$159.58	8.355%	$172.9129	$172.91	$172.90	$172.90
Purchase #4	$65.50	7.596%	$70.4754	$70.48	$70.50	$70.50
Purchase #5	$83.34	11.628%	$93.0308	$93.03	$93.05	$93.00
Purchase #6	$117.39	8.789%	$127.7074	$127.71	$127.70	$127.70
Purchase #7	$168.37	3.726%	$174.6435	$174.64	$174.65	$174.60
7 purchase totals =	$944.18		$1,025.5438	$1,025.55	$1,025.60	$1,025.40