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	$208.27	4.228%	$217.0757	$217.08	$217.10	$217.10
Purchase #2	$237.39	7.456%	$255.0898	$255.09	$255.10	$255.10
Purchase #3	$201.72	7.172%	$216.1874	$216.19	$216.20	$216.20
Purchase #4	$119.88	8.706%	$130.3168	$130.32	$130.30	$130.30
Purchase #5	$143.64	6.179%	$152.5155	$152.52	$152.50	$152.50
Purchase #6	$154.79	6.659%	$165.0975	$165.10	$165.10	$165.10
Purchase #7	$139.89	11.104%	$155.4234	$155.42	$155.40	$155.40
7 purchase totals =	$1,205.58		$1,291.7061	$1,291.72	$1,291.70	$1,291.70