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	$180.29	3.458%	$186.5244	$186.52	$186.50	$186.50
Purchase #2	$122.34	13.733%	$139.141	$139.14	$139.15	$139.10
Purchase #3	$220.62	3.746%	$228.8844	$228.88	$228.90	$228.90
Purchase #4	$159.89	3.438%	$165.387	$165.39	$165.40	$165.40
Purchase #5	$143.75	3.405%	$148.6447	$148.64	$148.65	$148.60
Purchase #6	$95.80	13.849%	$109.0673	$109.07	$109.05	$109.10
Purchase #7	$38.39	10.541%	$42.4367	$42.44	$42.45	$42.40
7 purchase totals =	$961.08		$1,020.0855	$1,020.08	$1,020.10	$1,020.00