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	$119.84	8.475%	$129.9964	$130.00	$130.00	$130.00
Purchase #2	$34.54	8.602%	$37.5111	$37.51	$37.50	$37.50
Purchase #3	$42.86	6.229%	$45.5297	$45.53	$45.55	$45.50
Purchase #4	$20.32	10.328%	$22.4186	$22.42	$22.40	$22.40
Purchase #5	$33.55	4.700%	$35.1269	$35.13	$35.15	$35.10
Purchase #6	$242.53	5.874%	$256.7762	$256.78	$256.80	$256.80
Purchase #7	$226.95	13.413%	$257.3908	$257.39	$257.40	$257.40
7 purchase totals =	$720.59		$784.7497	$784.76	$784.80	$784.70