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	$164.34	6.778%	$175.479	$175.48	$175.50	$175.50
Purchase #2	$186.85	10.414%	$206.3086	$206.31	$206.30	$206.30
Purchase #3	$14.70	9.331%	$16.0717	$16.07	$16.05	$16.10
Purchase #4	$142.38	7.274%	$152.7367	$152.74	$152.75	$152.70
Purchase #5	$196.31	10.394%	$216.7145	$216.71	$216.70	$216.70
Purchase #6	$107.69	3.635%	$111.6045	$111.60	$111.60	$111.60
Purchase #7	$139.25	11.645%	$155.4657	$155.47	$155.45	$155.50
7 purchase totals =	$951.52		$1,034.3807	$1,034.38	$1,034.35	$1,034.40