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	$55.96	6.520%	$59.6086	$59.61	$59.60	$59.60
Purchase #2	$67.86	13.155%	$76.787	$76.79	$76.80	$76.80
Purchase #3	$148.43	6.171%	$157.5896	$157.59	$157.60	$157.60
Purchase #4	$88.43	8.456%	$95.9076	$95.91	$95.90	$95.90
Purchase #5	$246.59	11.792%	$275.6679	$275.67	$275.65	$275.70
Purchase #6	$49.65	7.553%	$53.4001	$53.40	$53.40	$53.40
Purchase #7	$8.37	7.136%	$8.9673	$8.97	$8.95	$9.00
7 purchase totals =	$665.29		$727.9281	$727.94	$727.90	$728.00