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	$250.72	10.563%	$277.2036	$277.20	$277.20	$277.20
Purchase #2	$98.50	12.807%	$111.1149	$111.11	$111.10	$111.10
Purchase #3	$83.76	9.153%	$91.4266	$91.43	$91.45	$91.40
Purchase #4	$78.30	7.145%	$83.8945	$83.89	$83.90	$83.90
Purchase #5	$190.43	9.648%	$208.8027	$208.80	$208.80	$208.80
Purchase #6	$21.29	13.441%	$24.1516	$24.15	$24.15	$24.20
Purchase #7	$227.30	8.856%	$247.4297	$247.43	$247.45	$247.40
7 purchase totals =	$950.30		$1,044.0236	$1,044.01	$1,044.05	$1,044.00