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	$104.90	11.371%	$116.8282	$116.83	$116.85	$116.80
Purchase #2	$35.89	13.696%	$40.8055	$40.81	$40.80	$40.80
Purchase #3	$94.95	4.388%	$99.1164	$99.12	$99.10	$99.10
Purchase #4	$140.44	5.565%	$148.2555	$148.26	$148.25	$148.30
Purchase #5	$28.49	13.371%	$32.2994	$32.30	$32.30	$32.30
Purchase #6	$246.98	5.316%	$260.1095	$260.11	$260.10	$260.10
Purchase #7	$195.30	11.389%	$217.5427	$217.54	$217.55	$217.50
7 purchase totals =	$846.95		$914.9572	$914.97	$914.95	$914.90