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	$200.60	8.332%	$217.314	$217.31	$217.30	$217.30
Purchase #2	$150.32	3.659%	$155.8202	$155.82	$155.80	$155.80
Purchase #3	$152.39	11.430%	$169.8082	$169.81	$169.80	$169.80
Purchase #4	$82.77	3.869%	$85.9724	$85.97	$85.95	$86.00
Purchase #5	$35.25	7.702%	$37.965	$37.97	$37.95	$38.00
Purchase #6	$132.88	13.456%	$150.7603	$150.76	$150.75	$150.80
Purchase #7	$146.51	5.723%	$154.8948	$154.89	$154.90	$154.90
7 purchase totals =	$900.72		$972.5349	$972.53	$972.45	$972.60