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	$236.41	11.686%	$264.0369	$264.04	$264.05	$264.00
Purchase #2	$143.41	13.404%	$162.6327	$162.63	$162.65	$162.60
Purchase #3	$78.61	5.853%	$83.211	$83.21	$83.20	$83.20
Purchase #4	$63.54	13.172%	$71.9095	$71.91	$71.90	$71.90
Purchase #5	$7.25	4.568%	$7.5812	$7.58	$7.60	$7.60
Purchase #6	$208.89	12.466%	$234.9302	$234.93	$234.95	$234.90
Purchase #7	$218.99	5.872%	$231.8491	$231.85	$231.85	$231.80
7 purchase totals =	$957.10		$1,056.1506	$1,056.15	$1,056.20	$1,056.00