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	$132.66	10.725%	$146.8878	$146.89	$146.90	$146.90
Purchase #2	$54.65	7.223%	$58.5974	$58.60	$58.60	$58.60
Purchase #3	$48.58	10.518%	$53.6896	$53.69	$53.70	$53.70
Purchase #4	$161.60	6.143%	$171.5271	$171.53	$171.55	$171.50
Purchase #5	$18.97	5.507%	$20.0147	$20.01	$20.00	$20.00
Purchase #6	$96.41	13.313%	$109.2451	$109.25	$109.25	$109.20
Purchase #7	$243.74	12.807%	$274.9558	$274.96	$274.95	$275.00
7 purchase totals =	$756.61		$834.9175	$834.93	$834.95	$834.90