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	$234.82	10.105%	$258.5486	$258.55	$258.55	$258.50
Purchase #2	$82.73	8.318%	$89.6115	$89.61	$89.60	$89.60
Purchase #3	$55.94	7.430%	$60.0963	$60.10	$60.10	$60.10
Purchase #4	$244.33	13.686%	$277.769	$277.77	$277.75	$277.80
Purchase #5	$102.42	12.561%	$115.285	$115.29	$115.30	$115.30
Purchase #6	$198.77	4.628%	$207.9691	$207.97	$207.95	$208.00
Purchase #7	$135.32	4.857%	$141.8925	$141.89	$141.90	$141.90
7 purchase totals =	$1,054.33		$1,151.1720	$1,151.18	$1,151.15	$1,151.20