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	$241.90	3.671%	$250.7801	$250.78	$250.80	$250.80
Purchase #2	$20.99	3.417%	$21.7072	$21.71	$21.70	$21.70
Purchase #3	$60.58	10.667%	$67.0421	$67.04	$67.05	$67.00
Purchase #4	$76.93	13.231%	$87.1086	$87.11	$87.10	$87.10
Purchase #5	$111.70	4.217%	$116.4104	$116.41	$116.40	$116.40
Purchase #6	$68.83	7.181%	$73.7727	$73.77	$73.75	$73.80
Purchase #7	$117.41	5.368%	$123.7126	$123.71	$123.70	$123.70
7 purchase totals =	$698.34		$740.5337	$740.53	$740.50	$740.50