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	$213.72	4.150%	$222.5894	$222.59	$222.60	$222.60
Purchase #2	$93.32	8.795%	$101.5275	$101.53	$101.55	$101.50
Purchase #3	$107.35	10.690%	$118.8257	$118.83	$118.85	$118.80
Purchase #4	$74.58	4.862%	$78.2061	$78.21	$78.20	$78.20
Purchase #5	$197.56	4.725%	$206.8947	$206.89	$206.90	$206.90
Purchase #6	$22.56	3.675%	$23.3891	$23.39	$23.40	$23.40
Purchase #7	$35.47	11.647%	$39.6012	$39.60	$39.60	$39.60
7 purchase totals =	$744.56		$791.0337	$791.04	$791.10	$791.00