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	$236.93	9.698%	$259.9075	$259.91	$259.90	$259.90
Purchase #2	$152.75	8.375%	$165.5428	$165.54	$165.55	$165.50
Purchase #3	$160.86	7.240%	$172.5063	$172.51	$172.50	$172.50
Purchase #4	$108.44	7.444%	$116.5123	$116.51	$116.50	$116.50
Purchase #5	$73.55	8.628%	$79.8959	$79.90	$79.90	$79.90
Purchase #6	$189.49	10.621%	$209.6157	$209.62	$209.60	$209.60
Purchase #7	$85.52	8.252%	$92.5771	$92.58	$92.60	$92.60
7 purchase totals =	$1,007.54		$1,096.5576	$1,096.57	$1,096.55	$1,096.50