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	$30.75	9.665%	$33.722	$33.72	$33.70	$33.70
Purchase #2	$127.87	7.851%	$137.9091	$137.91	$137.90	$137.90
Purchase #3	$229.66	7.622%	$247.1647	$247.16	$247.15	$247.20
Purchase #4	$156.47	12.763%	$176.4403	$176.44	$176.45	$176.40
Purchase #5	$114.82	10.683%	$127.0862	$127.09	$127.10	$127.10
Purchase #6	$250.31	7.529%	$269.1558	$269.16	$269.15	$269.20
Purchase #7	$147.74	3.446%	$152.8311	$152.83	$152.85	$152.80
7 purchase totals =	$1,057.62		$1,144.3092	$1,144.31	$1,144.30	$1,144.30