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	$245.65	4.539%	$256.8001	$256.80	$256.80	$256.80
Purchase #2	$160.83	11.339%	$179.0665	$179.07	$179.05	$179.10
Purchase #3	$156.74	10.227%	$172.7698	$172.77	$172.75	$172.80
Purchase #4	$220.90	7.659%	$237.8187	$237.82	$237.80	$237.80
Purchase #5	$87.41	12.311%	$98.171	$98.17	$98.15	$98.20
Purchase #6	$149.55	7.350%	$160.5419	$160.54	$160.55	$160.50
Purchase #7	$41.75	8.869%	$45.4528	$45.45	$45.45	$45.50
7 purchase totals =	$1,062.83		$1,150.6208	$1,150.62	$1,150.55	$1,150.70