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	$59.47	3.450%	$61.5217	$61.52	$61.50	$61.50
Purchase #2	$228.57	5.803%	$241.8339	$241.83	$241.85	$241.80
Purchase #3	$148.33	6.333%	$157.7237	$157.72	$157.70	$157.70
Purchase #4	$217.47	11.263%	$241.9636	$241.96	$241.95	$242.00
Purchase #5	$60.46	10.174%	$66.6112	$66.61	$66.60	$66.60
Purchase #6	$134.51	13.369%	$152.4926	$152.49	$152.50	$152.50
Purchase #7	$187.79	6.806%	$200.571	$200.57	$200.55	$200.60
7 purchase totals =	$1,036.60		$1,122.7177	$1,122.70	$1,122.65	$1,122.70