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	$228.34	5.717%	$241.3942	$241.39	$241.40	$241.40
Purchase #2	$116.84	13.430%	$132.5316	$132.53	$132.55	$132.50
Purchase #3	$86.34	4.761%	$90.4506	$90.45	$90.45	$90.50
Purchase #4	$44.95	4.287%	$46.877	$46.88	$46.90	$46.90
Purchase #5	$132.77	5.853%	$140.541	$140.54	$140.55	$140.50
Purchase #6	$166.73	3.781%	$173.0341	$173.03	$173.05	$173.00
Purchase #7	$138.73	6.402%	$147.6115	$147.61	$147.60	$147.60
7 purchase totals =	$914.70		$972.4400	$972.43	$972.50	$972.40