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	$248.37	6.698%	$265.0058	$265.01	$265.00	$265.00
Purchase #2	$249.36	10.494%	$275.5278	$275.53	$275.55	$275.50
Purchase #3	$125.38	12.551%	$141.1164	$141.12	$141.10	$141.10
Purchase #4	$239.25	11.369%	$266.4503	$266.45	$266.45	$266.50
Purchase #5	$36.78	4.629%	$38.4825	$38.48	$38.50	$38.50
Purchase #6	$12.74	4.446%	$13.3064	$13.31	$13.30	$13.30
Purchase #7	$137.71	10.229%	$151.7964	$151.80	$151.80	$151.80
7 purchase totals =	$1,049.59		$1,151.6856	$1,151.70	$1,151.70	$1,151.70