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	$134.72	10.628%	$149.038	$149.04	$149.05	$149.00
Purchase #2	$131.80	10.518%	$145.6627	$145.66	$145.65	$145.70
Purchase #3	$6.54	12.357%	$7.3481	$7.35	$7.35	$7.30
Purchase #4	$196.44	6.138%	$208.4975	$208.50	$208.50	$208.50
Purchase #5	$93.77	7.291%	$100.6068	$100.61	$100.60	$100.60
Purchase #6	$34.35	9.791%	$37.7132	$37.71	$37.70	$37.70
Purchase #7	$240.90	10.379%	$265.903	$265.90	$265.90	$265.90
7 purchase totals =	$838.52		$914.7693	$914.77	$914.75	$914.70