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	$213.52	3.452%	$220.8907	$220.89	$220.90	$220.90
Purchase #2	$113.35	11.250%	$126.1019	$126.10	$126.10	$126.10
Purchase #3	$58.61	11.810%	$65.5318	$65.53	$65.55	$65.50
Purchase #4	$58.50	11.662%	$65.3223	$65.32	$65.30	$65.30
Purchase #5	$163.67	13.451%	$185.6853	$185.69	$185.70	$185.70
Purchase #6	$197.30	8.406%	$213.885	$213.89	$213.90	$213.90
Purchase #7	$238.81	13.508%	$271.0685	$271.07	$271.05	$271.10
7 purchase totals =	$1,043.76		$1,148.4855	$1,148.49	$1,148.50	$1,148.50