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	$124.84	4.483%	$130.4366	$130.44	$130.45	$130.40
Purchase #2	$80.89	7.586%	$87.0263	$87.03	$87.05	$87.00
Purchase #3	$19.79	10.300%	$21.8284	$21.83	$21.85	$21.80
Purchase #4	$186.98	7.350%	$200.723	$200.72	$200.70	$200.70
Purchase #5	$58.31	10.651%	$64.5206	$64.52	$64.50	$64.50
Purchase #6	$24.59	3.857%	$25.5384	$25.54	$25.55	$25.50
Purchase #7	$248.28	3.469%	$256.8928	$256.89	$256.90	$256.90
7 purchase totals =	$743.68		$786.9661	$786.97	$787.00	$786.80