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	$78.92	13.373%	$89.474	$89.47	$89.45	$89.50
Purchase #2	$12.30	4.119%	$12.8066	$12.81	$12.80	$12.80
Purchase #3	$230.75	13.657%	$262.2635	$262.26	$262.25	$262.30
Purchase #4	$117.37	5.390%	$123.6962	$123.70	$123.70	$123.70
Purchase #5	$141.65	7.818%	$152.7242	$152.72	$152.70	$152.70
Purchase #6	$187.41	12.767%	$211.3366	$211.34	$211.35	$211.30
Purchase #7	$182.42	11.561%	$203.5096	$203.51	$203.50	$203.50
7 purchase totals =	$950.82		$1,055.8107	$1,055.81	$1,055.75	$1,055.80