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	$223.89	6.681%	$238.8481	$238.85	$238.85	$238.80
Purchase #2	$71.57	8.534%	$77.6778	$77.68	$77.70	$77.70
Purchase #3	$244.54	6.531%	$260.5109	$260.51	$260.50	$260.50
Purchase #4	$242.60	4.297%	$253.0245	$253.02	$253.00	$253.00
Purchase #5	$124.33	12.343%	$139.6761	$139.68	$139.70	$139.70
Purchase #6	$155.33	4.299%	$162.0076	$162.01	$162.00	$162.00
Purchase #7	$77.59	6.573%	$82.69	$82.69	$82.70	$82.70
7 purchase totals =	$1,139.85		$1,214.4350	$1,214.44	$1,214.45	$1,214.40