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	$248.82	10.742%	$275.5482	$275.55	$275.55	$275.50
Purchase #2	$224.40	13.232%	$254.0926	$254.09	$254.10	$254.10
Purchase #3	$216.59	12.443%	$243.5403	$243.54	$243.55	$243.50
Purchase #4	$40.46	13.192%	$45.7975	$45.80	$45.80	$45.80
Purchase #5	$154.50	5.435%	$162.8971	$162.90	$162.90	$162.90
Purchase #6	$202.91	11.126%	$225.4858	$225.49	$225.50	$225.50
Purchase #7	$13.63	11.255%	$15.1641	$15.16	$15.15	$15.20
7 purchase totals =	$1,101.31		$1,222.5256	$1,222.53	$1,222.55	$1,222.50