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	$127.61	3.397%	$131.9449	$131.94	$131.95	$131.90
Purchase #2	$171.48	11.587%	$191.3494	$191.35	$191.35	$191.30
Purchase #3	$182.48	13.762%	$207.5929	$207.59	$207.60	$207.60
Purchase #4	$213.43	13.706%	$242.6827	$242.68	$242.70	$242.70
Purchase #5	$64.92	12.268%	$72.8844	$72.88	$72.90	$72.90
Purchase #6	$10.37	12.642%	$11.681	$11.68	$11.70	$11.70
Purchase #7	$82.86	6.680%	$88.395	$88.40	$88.40	$88.40
7 purchase totals =	$853.15		$946.5303	$946.52	$946.60	$946.50