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	$146.37	3.729%	$151.8281	$151.83	$151.85	$151.80
Purchase #2	$241.47	8.439%	$261.8477	$261.85	$261.85	$261.80
Purchase #3	$60.27	9.503%	$65.9975	$66.00	$66.00	$66.00
Purchase #4	$77.57	3.412%	$80.2167	$80.22	$80.20	$80.20
Purchase #5	$36.29	4.414%	$37.8918	$37.89	$37.90	$37.90
Purchase #6	$201.45	10.314%	$222.2276	$222.23	$222.25	$222.20
Purchase #7	$222.80	12.431%	$250.4963	$250.50	$250.50	$250.50
7 purchase totals =	$986.22		$1,070.5057	$1,070.52	$1,070.55	$1,070.40