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	$235.92	8.643%	$256.3106	$256.31	$256.30	$256.30
Purchase #2	$57.67	13.103%	$65.2265	$65.23	$65.25	$65.20
Purchase #3	$36.40	11.506%	$40.5882	$40.59	$40.60	$40.60
Purchase #4	$211.67	11.367%	$235.7305	$235.73	$235.75	$235.70
Purchase #5	$84.47	11.291%	$94.0075	$94.01	$94.00	$94.00
Purchase #6	$224.71	8.367%	$243.5115	$243.51	$243.50	$243.50
Purchase #7	$182.62	5.330%	$192.3536	$192.35	$192.35	$192.40
7 purchase totals =	$1,033.46		$1,127.7284	$1,127.73	$1,127.75	$1,127.70