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	$57.44	7.541%	$61.7716	$61.77	$61.75	$61.80
Purchase #2	$47.76	8.410%	$51.7766	$51.78	$51.80	$51.80
Purchase #3	$98.78	13.357%	$111.974	$111.97	$111.95	$112.00
Purchase #4	$237.63	11.152%	$264.1305	$264.13	$264.15	$264.10
Purchase #5	$157.66	7.559%	$169.5775	$169.58	$169.60	$169.60
Purchase #6	$164.60	4.517%	$172.035	$172.04	$172.05	$172.00
Purchase #7	$146.68	10.329%	$161.8306	$161.83	$161.85	$161.80
7 purchase totals =	$910.55		$993.0958	$993.10	$993.15	$993.10