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	$193.25	11.806%	$216.0651	$216.07	$216.05	$216.10
Purchase #2	$125.73	13.105%	$142.2069	$142.21	$142.20	$142.20
Purchase #3	$112.50	13.215%	$127.3669	$127.37	$127.35	$127.40
Purchase #4	$152.60	8.243%	$165.1788	$165.18	$165.20	$165.20
Purchase #5	$70.72	9.121%	$77.1704	$77.17	$77.15	$77.20
Purchase #6	$247.77	8.392%	$268.5629	$268.56	$268.55	$268.60
Purchase #7	$119.82	9.242%	$130.8938	$130.89	$130.90	$130.90
7 purchase totals =	$1,022.39		$1,127.4448	$1,127.45	$1,127.40	$1,127.60