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	$235.71	11.815%	$263.5591	$263.56	$263.55	$263.60
Purchase #2	$220.87	4.200%	$230.1465	$230.15	$230.15	$230.10
Purchase #3	$127.96	5.108%	$134.4962	$134.50	$134.50	$134.50
Purchase #4	$152.62	8.496%	$165.5866	$165.59	$165.60	$165.60
Purchase #5	$118.77	12.566%	$133.6946	$133.69	$133.70	$133.70
Purchase #6	$94.54	8.477%	$102.5542	$102.55	$102.55	$102.60
Purchase #7	$64.47	3.699%	$66.8547	$66.85	$66.85	$66.90
7 purchase totals =	$1,014.94		$1,096.8919	$1,096.89	$1,096.90	$1,097.00