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	$81.42	7.198%	$87.2806	$87.28	$87.30	$87.30
Purchase #2	$223.77	12.381%	$251.475	$251.48	$251.50	$251.50
Purchase #3	$76.60	4.605%	$80.1274	$80.13	$80.15	$80.10
Purchase #4	$244.27	6.167%	$259.3341	$259.33	$259.35	$259.30
Purchase #5	$75.79	3.254%	$78.2562	$78.26	$78.25	$78.30
Purchase #6	$144.41	11.682%	$161.28	$161.28	$161.30	$161.30
Purchase #7	$94.71	7.250%	$101.5765	$101.58	$101.60	$101.60
7 purchase totals =	$940.97		$1,019.3298	$1,019.34	$1,019.45	$1,019.40