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	$33.92	3.758%	$35.1947	$35.19	$35.20	$35.20
Purchase #2	$68.70	13.853%	$78.217	$78.22	$78.20	$78.20
Purchase #3	$11.34	4.843%	$11.8892	$11.89	$11.90	$11.90
Purchase #4	$224.68	6.610%	$239.5313	$239.53	$239.55	$239.50
Purchase #5	$160.29	7.725%	$172.6724	$172.67	$172.65	$172.70
Purchase #6	$46.25	9.120%	$50.468	$50.47	$50.45	$50.50
Purchase #7	$86.56	3.178%	$89.3109	$89.31	$89.30	$89.30
7 purchase totals =	$631.74		$677.2835	$677.28	$677.25	$677.30