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	$102.87	8.823%	$111.9462	$111.95	$111.95	$111.90
Purchase #2	$33.72	11.341%	$37.5442	$37.54	$37.55	$37.50
Purchase #3	$80.97	10.192%	$89.2225	$89.22	$89.20	$89.20
Purchase #4	$75.44	9.578%	$82.6656	$82.67	$82.65	$82.70
Purchase #5	$202.85	12.656%	$228.5227	$228.52	$228.50	$228.50
Purchase #6	$141.88	13.749%	$161.3871	$161.39	$161.40	$161.40
Purchase #7	$97.52	3.347%	$100.784	$100.78	$100.80	$100.80
7 purchase totals =	$735.25		$812.0723	$812.07	$812.05	$812.00