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	$47.34	12.182%	$53.107	$53.11	$53.10	$53.10
Purchase #2	$175.43	9.205%	$191.5783	$191.58	$191.60	$191.60
Purchase #3	$83.76	9.675%	$91.8638	$91.86	$91.85	$91.90
Purchase #4	$156.57	8.246%	$169.4808	$169.48	$169.50	$169.50
Purchase #5	$180.27	5.516%	$190.2137	$190.21	$190.20	$190.20
Purchase #6	$59.27	4.306%	$61.8222	$61.82	$61.80	$61.80
Purchase #7	$94.40	10.162%	$103.9929	$103.99	$104.00	$104.00
7 purchase totals =	$797.04		$862.0587	$862.05	$862.05	$862.10