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	$95.81	4.191%	$99.8254	$99.83	$99.85	$99.80
Purchase #2	$166.87	13.679%	$189.6961	$189.70	$189.70	$189.70
Purchase #3	$195.74	9.573%	$214.4782	$214.48	$214.50	$214.50
Purchase #4	$121.53	13.285%	$137.6753	$137.68	$137.70	$137.70
Purchase #5	$111.42	4.498%	$116.4317	$116.43	$116.45	$116.40
Purchase #6	$168.64	8.864%	$183.5882	$183.59	$183.60	$183.60
Purchase #7	$143.64	6.316%	$152.7123	$152.71	$152.70	$152.70
7 purchase totals =	$1,003.65		$1,094.4072	$1,094.42	$1,094.50	$1,094.40