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	$202.82	6.574%	$216.1534	$216.15	$216.15	$216.20
Purchase #2	$153.55	5.583%	$162.1227	$162.12	$162.10	$162.10
Purchase #3	$125.90	3.857%	$130.756	$130.76	$130.75	$130.80
Purchase #4	$79.54	4.402%	$83.0414	$83.04	$83.05	$83.00
Purchase #5	$53.76	10.406%	$59.3543	$59.35	$59.35	$59.40
Purchase #6	$70.59	5.377%	$74.3856	$74.39	$74.40	$74.40
Purchase #7	$124.76	12.794%	$140.7218	$140.72	$140.70	$140.70
7 purchase totals =	$810.92		$866.5352	$866.53	$866.50	$866.60