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	$246.89	7.727%	$265.9672	$265.97	$265.95	$266.00
Purchase #2	$11.46	7.179%	$12.2827	$12.28	$12.30	$12.30
Purchase #3	$93.90	12.325%	$105.4732	$105.47	$105.45	$105.50
Purchase #4	$241.59	9.183%	$263.7752	$263.78	$263.80	$263.80
Purchase #5	$12.48	10.446%	$13.7837	$13.78	$13.80	$13.80
Purchase #6	$241.37	13.293%	$273.4553	$273.46	$273.45	$273.50
Purchase #7	$38.94	4.491%	$40.6888	$40.69	$40.70	$40.70
7 purchase totals =	$886.63		$975.4261	$975.43	$975.45	$975.60