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	$130.42	7.795%	$140.5862	$140.59	$140.60	$140.60
Purchase #2	$90.62	5.830%	$95.9031	$95.90	$95.90	$95.90
Purchase #3	$94.57	5.603%	$99.8688	$99.87	$99.85	$99.90
Purchase #4	$16.79	10.799%	$18.6032	$18.60	$18.60	$18.60
Purchase #5	$85.56	8.557%	$92.8814	$92.88	$92.90	$92.90
Purchase #6	$137.90	8.126%	$149.1058	$149.11	$149.10	$149.10
Purchase #7	$234.42	13.188%	$265.3353	$265.34	$265.35	$265.30
7 purchase totals =	$790.28		$862.2838	$862.29	$862.30	$862.30