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	$217.83	11.553%	$242.9959	$243.00	$243.00	$243.00
Purchase #2	$65.60	13.542%	$74.4836	$74.48	$74.50	$74.50
Purchase #3	$102.52	13.480%	$116.3397	$116.34	$116.35	$116.30
Purchase #4	$58.52	12.375%	$65.7619	$65.76	$65.75	$65.80
Purchase #5	$220.72	12.306%	$247.8818	$247.88	$247.90	$247.90
Purchase #6	$106.66	4.646%	$111.6154	$111.62	$111.60	$111.60
Purchase #7	$231.72	9.565%	$253.884	$253.88	$253.90	$253.90
7 purchase totals =	$1,003.57		$1,112.9623	$1,112.96	$1,113.00	$1,113.00