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	$94.38	11.606%	$105.3337	$105.33	$105.35	$105.30
Purchase #2	$206.94	10.123%	$227.8885	$227.89	$227.90	$227.90
Purchase #3	$160.82	7.341%	$172.6258	$172.63	$172.65	$172.60
Purchase #4	$50.61	13.282%	$57.332	$57.33	$57.35	$57.30
Purchase #5	$22.69	10.573%	$25.089	$25.09	$25.10	$25.10
Purchase #6	$223.84	7.539%	$240.7153	$240.72	$240.70	$240.70
Purchase #7	$97.41	5.160%	$102.4364	$102.44	$102.45	$102.40
7 purchase totals =	$856.69		$931.4207	$931.43	$931.50	$931.30