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	$30.73	8.785%	$33.4296	$33.43	$33.45	$33.40
Purchase #2	$200.80	11.500%	$223.892	$223.89	$223.90	$223.90
Purchase #3	$118.77	11.860%	$132.8561	$132.86	$132.85	$132.90
Purchase #4	$237.66	7.137%	$254.6218	$254.62	$254.60	$254.60
Purchase #5	$138.33	8.643%	$150.2859	$150.29	$150.30	$150.30
Purchase #6	$125.47	6.387%	$133.4838	$133.48	$133.50	$133.50
Purchase #7	$89.68	13.779%	$102.037	$102.04	$102.05	$102.00
7 purchase totals =	$941.44		$1,030.6062	$1,030.61	$1,030.65	$1,030.60