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	$202.31	3.537%	$209.4657	$209.47	$209.45	$209.50
Purchase #2	$104.82	4.493%	$109.5296	$109.53	$109.55	$109.50
Purchase #3	$11.33	9.684%	$12.4272	$12.43	$12.45	$12.40
Purchase #4	$97.31	8.770%	$105.8441	$105.84	$105.85	$105.80
Purchase #5	$149.34	13.597%	$169.6458	$169.65	$169.65	$169.60
Purchase #6	$123.33	11.574%	$137.6042	$137.60	$137.60	$137.60
Purchase #7	$234.91	6.604%	$250.4235	$250.42	$250.40	$250.40
7 purchase totals =	$923.35		$994.9401	$994.94	$994.95	$994.80