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	$148.40	13.670%	$168.6863	$168.69	$168.70	$168.70
Purchase #2	$137.47	10.463%	$151.8535	$151.85	$151.85	$151.90
Purchase #3	$37.58	12.803%	$42.3914	$42.39	$42.40	$42.40
Purchase #4	$138.81	8.457%	$150.5492	$150.55	$150.55	$150.50
Purchase #5	$152.53	11.695%	$170.3684	$170.37	$170.35	$170.40
Purchase #6	$103.66	7.359%	$111.2883	$111.29	$111.30	$111.30
Purchase #7	$161.55	6.176%	$171.5273	$171.53	$171.55	$171.50
7 purchase totals =	$880.00		$966.6644	$966.67	$966.70	$966.70