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	$192.68	13.558%	$218.8036	$218.80	$218.80	$218.80
Purchase #2	$28.51	3.672%	$29.5569	$29.56	$29.55	$29.60
Purchase #3	$95.29	5.433%	$100.4671	$100.47	$100.45	$100.50
Purchase #4	$207.72	13.539%	$235.8432	$235.84	$235.85	$235.80
Purchase #5	$240.95	8.825%	$262.2138	$262.21	$262.20	$262.20
Purchase #6	$43.76	4.465%	$45.7139	$45.71	$45.70	$45.70
Purchase #7	$135.56	13.520%	$153.8877	$153.89	$153.90	$153.90
7 purchase totals =	$944.47		$1,046.4862	$1,046.48	$1,046.45	$1,046.50