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	$146.39	13.674%	$166.4074	$166.41	$166.40	$166.40
Purchase #2	$63.53	4.467%	$66.3679	$66.37	$66.35	$66.40
Purchase #3	$168.57	4.172%	$175.6027	$175.60	$175.60	$175.60
Purchase #4	$220.52	11.252%	$245.3329	$245.33	$245.35	$245.30
Purchase #5	$76.70	7.498%	$82.451	$82.45	$82.45	$82.50
Purchase #6	$244.67	3.126%	$252.3184	$252.32	$252.30	$252.30
Purchase #7	$92.25	5.310%	$97.1485	$97.15	$97.15	$97.10
7 purchase totals =	$1,012.63		$1,085.6288	$1,085.63	$1,085.60	$1,085.60