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	$53.76	10.703%	$59.5139	$59.51	$59.50	$59.50
Purchase #2	$140.43	3.475%	$145.3099	$145.31	$145.30	$145.30
Purchase #3	$88.85	7.850%	$95.8247	$95.82	$95.80	$95.80
Purchase #4	$242.92	7.667%	$261.5447	$261.54	$261.55	$261.50
Purchase #5	$172.89	9.447%	$189.2229	$189.22	$189.20	$189.20
Purchase #6	$145.40	4.368%	$151.7511	$151.75	$151.75	$151.80
Purchase #7	$111.30	7.596%	$119.7543	$119.75	$119.75	$119.80
7 purchase totals =	$955.55		$1,022.9215	$1,022.90	$1,022.85	$1,022.90