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	$92.54	7.524%	$99.5027	$99.50	$99.50	$99.50
Purchase #2	$150.84	3.115%	$155.5387	$155.54	$155.55	$155.50
Purchase #3	$184.47	3.310%	$190.576	$190.58	$190.60	$190.60
Purchase #4	$231.78	8.346%	$251.1244	$251.12	$251.10	$251.10
Purchase #5	$44.84	8.521%	$48.6608	$48.66	$48.65	$48.70
Purchase #6	$196.49	3.373%	$203.1176	$203.12	$203.10	$203.10
Purchase #7	$53.38	11.667%	$59.6078	$59.61	$59.60	$59.60
7 purchase totals =	$954.34		$1,008.1280	$1,008.13	$1,008.10	$1,008.10