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	$182.78	7.119%	$195.7921	$195.79	$195.80	$195.80
Purchase #2	$215.97	10.470%	$238.5821	$238.58	$238.60	$238.60
Purchase #3	$182.87	9.640%	$200.4987	$200.50	$200.50	$200.50
Purchase #4	$128.93	8.174%	$139.4687	$139.47	$139.45	$139.50
Purchase #5	$154.64	13.644%	$175.7391	$175.74	$175.75	$175.70
Purchase #6	$38.86	8.273%	$42.0749	$42.07	$42.05	$42.10
Purchase #7	$197.75	13.437%	$224.3217	$224.32	$224.30	$224.30
7 purchase totals =	$1,101.80		$1,216.4773	$1,216.47	$1,216.45	$1,216.50