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	$123.43	7.479%	$132.6613	$132.66	$132.65	$132.70
Purchase #2	$53.75	11.353%	$59.8522	$59.85	$59.85	$59.90
Purchase #3	$130.32	12.325%	$146.3819	$146.38	$146.40	$146.40
Purchase #4	$198.53	10.675%	$219.7231	$219.72	$219.70	$219.70
Purchase #5	$32.74	12.350%	$36.7834	$36.78	$36.80	$36.80
Purchase #6	$215.87	3.244%	$222.8728	$222.87	$222.85	$222.90
Purchase #7	$12.92	6.442%	$13.7523	$13.75	$13.75	$13.80
7 purchase totals =	$767.56		$832.0270	$832.01	$832.00	$832.20