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	$122.28	11.618%	$136.4865	$136.49	$136.50	$136.50
Purchase #2	$227.57	7.435%	$244.4898	$244.49	$244.50	$244.50
Purchase #3	$144.46	4.466%	$150.9116	$150.91	$150.90	$150.90
Purchase #4	$138.79	5.567%	$146.5164	$146.52	$146.50	$146.50
Purchase #5	$108.53	8.777%	$118.0557	$118.06	$118.05	$118.10
Purchase #6	$142.45	6.268%	$151.3788	$151.38	$151.40	$151.40
Purchase #7	$77.89	13.634%	$88.5095	$88.51	$88.50	$88.50
7 purchase totals =	$961.97		$1,036.3483	$1,036.36	$1,036.35	$1,036.40