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	$238.47	7.736%	$256.918	$256.92	$256.90	$256.90
Purchase #2	$144.67	12.626%	$162.936	$162.94	$162.95	$162.90
Purchase #3	$113.64	9.301%	$124.2097	$124.21	$124.20	$124.20
Purchase #4	$142.94	10.349%	$157.7329	$157.73	$157.75	$157.70
Purchase #5	$249.25	6.672%	$265.88	$265.88	$265.90	$265.90
Purchase #6	$135.73	8.336%	$147.0445	$147.04	$147.05	$147.00
Purchase #7	$28.89	11.352%	$32.1696	$32.17	$32.15	$32.20
7 purchase totals =	$1,053.59		$1,146.8907	$1,146.89	$1,146.90	$1,146.80