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	$53.98	12.214%	$60.5731	$60.57	$60.55	$60.60
Purchase #2	$159.31	8.398%	$172.6889	$172.69	$172.70	$172.70
Purchase #3	$197.58	12.812%	$222.8939	$222.89	$222.90	$222.90
Purchase #4	$152.26	13.172%	$172.3157	$172.32	$172.30	$172.30
Purchase #5	$169.37	13.450%	$192.1503	$192.15	$192.15	$192.20
Purchase #6	$33.87	3.656%	$35.1083	$35.11	$35.10	$35.10
Purchase #7	$196.57	13.108%	$222.3364	$222.34	$222.35	$222.30
7 purchase totals =	$962.94		$1,078.0666	$1,078.07	$1,078.05	$1,078.10