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	$158.73	6.781%	$169.4935	$169.49	$169.50	$169.50
Purchase #2	$133.54	3.289%	$137.9321	$137.93	$137.95	$137.90
Purchase #3	$20.59	4.640%	$21.5454	$21.55	$21.55	$21.50
Purchase #4	$11.81	11.224%	$13.1356	$13.14	$13.15	$13.10
Purchase #5	$59.37	11.544%	$66.2237	$66.22	$66.20	$66.20
Purchase #6	$144.32	9.418%	$157.9121	$157.91	$157.90	$157.90
Purchase #7	$183.30	8.521%	$198.919	$198.92	$198.90	$198.90
7 purchase totals =	$711.66		$765.1614	$765.16	$765.15	$765.00