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	$133.76	5.606%	$141.2586	$141.26	$141.25	$141.30
Purchase #2	$9.30	3.394%	$9.6156	$9.62	$9.60	$9.60
Purchase #3	$242.85	8.731%	$264.0532	$264.05	$264.05	$264.10
Purchase #4	$222.93	12.452%	$250.6892	$250.69	$250.70	$250.70
Purchase #5	$195.84	6.868%	$209.2903	$209.29	$209.30	$209.30
Purchase #6	$121.93	4.547%	$127.4742	$127.47	$127.45	$127.50
Purchase #7	$39.89	6.567%	$42.5096	$42.51	$42.50	$42.50
7 purchase totals =	$966.50		$1,044.8907	$1,044.89	$1,044.85	$1,045.00