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	$199.45	6.665%	$212.7433	$212.74	$212.75	$212.70
Purchase #2	$125.60	4.123%	$130.7785	$130.78	$130.80	$130.80
Purchase #3	$241.89	13.498%	$274.5403	$274.54	$274.55	$274.50
Purchase #4	$218.43	4.599%	$228.4756	$228.48	$228.50	$228.50
Purchase #5	$128.94	6.763%	$137.6602	$137.66	$137.65	$137.70
Purchase #6	$82.58	4.659%	$86.4274	$86.43	$86.45	$86.40
Purchase #7	$171.26	11.171%	$190.3915	$190.39	$190.40	$190.40
7 purchase totals =	$1,168.15		$1,261.0168	$1,261.02	$1,261.10	$1,261.00