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	$178.83	6.757%	$190.9135	$190.91	$190.90	$190.90
Purchase #2	$148.27	11.389%	$165.1565	$165.16	$165.15	$165.20
Purchase #3	$59.36	3.758%	$61.5907	$61.59	$61.60	$61.60
Purchase #4	$243.42	7.365%	$261.3479	$261.35	$261.35	$261.30
Purchase #5	$35.74	13.618%	$40.6071	$40.61	$40.60	$40.60
Purchase #6	$158.82	5.805%	$168.0395	$168.04	$168.05	$168.00
Purchase #7	$64.77	4.313%	$67.5635	$67.56	$67.55	$67.60
7 purchase totals =	$889.21		$955.2187	$955.22	$955.20	$955.20