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	$160.62	4.653%	$168.0936	$168.09	$168.10	$168.10
Purchase #2	$65.79	7.723%	$70.871	$70.87	$70.85	$70.90
Purchase #3	$248.68	8.815%	$270.6011	$270.60	$270.60	$270.60
Purchase #4	$151.39	5.610%	$159.883	$159.88	$159.90	$159.90
Purchase #5	$243.89	5.197%	$256.565	$256.57	$256.55	$256.60
Purchase #6	$169.63	12.576%	$190.9627	$190.96	$190.95	$191.00
Purchase #7	$158.58	13.279%	$179.6378	$179.64	$179.65	$179.60
7 purchase totals =	$1,198.58		$1,296.6142	$1,296.61	$1,296.60	$1,296.70