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	$61.53	4.165%	$64.0927	$64.09	$64.10	$64.10
Purchase #2	$98.65	13.457%	$111.9253	$111.93	$111.95	$111.90
Purchase #3	$60.61	9.693%	$66.4849	$66.48	$66.50	$66.50
Purchase #4	$93.53	10.681%	$103.5199	$103.52	$103.50	$103.50
Purchase #5	$107.64	7.768%	$116.0015	$116.00	$116.00	$116.00
Purchase #6	$244.48	4.508%	$255.5012	$255.50	$255.50	$255.50
Purchase #7	$219.78	6.492%	$234.0481	$234.05	$234.05	$234.00
7 purchase totals =	$886.22		$951.5736	$951.57	$951.60	$951.50