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	$31.42	3.589%	$32.5477	$32.55	$32.55	$32.50
Purchase #2	$99.97	6.117%	$106.0852	$106.09	$106.10	$106.10
Purchase #3	$154.77	7.562%	$166.4737	$166.47	$166.45	$166.50
Purchase #4	$62.73	6.659%	$66.9072	$66.91	$66.90	$66.90
Purchase #5	$190.48	7.868%	$205.467	$205.47	$205.45	$205.50
Purchase #6	$63.76	3.323%	$65.8787	$65.88	$65.90	$65.90
Purchase #7	$138.42	13.428%	$157.007	$157.01	$157.00	$157.00
7 purchase totals =	$741.55		$800.3665	$800.38	$800.35	$800.40