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	$191.65	4.297%	$199.8852	$199.89	$199.90	$199.90
Purchase #2	$13.25	8.469%	$14.3721	$14.37	$14.35	$14.40
Purchase #3	$130.48	10.813%	$144.5888	$144.59	$144.60	$144.60
Purchase #4	$56.66	6.371%	$60.2698	$60.27	$60.25	$60.30
Purchase #5	$230.61	13.114%	$260.8522	$260.85	$260.85	$260.90
Purchase #6	$53.75	6.687%	$57.3443	$57.34	$57.35	$57.30
Purchase #7	$90.56	4.409%	$94.5528	$94.55	$94.55	$94.60
7 purchase totals =	$766.96		$831.8652	$831.86	$831.85	$832.00