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	$127.30	13.800%	$144.8674	$144.87	$144.85	$144.90
Purchase #2	$174.87	3.389%	$180.7963	$180.80	$180.80	$180.80
Purchase #3	$14.89	5.849%	$15.7609	$15.76	$15.75	$15.80
Purchase #4	$80.54	11.775%	$90.0236	$90.02	$90.00	$90.00
Purchase #5	$234.56	13.779%	$266.88	$266.88	$266.90	$266.90
Purchase #6	$137.44	12.604%	$154.7629	$154.76	$154.75	$154.80
Purchase #7	$242.44	7.770%	$261.2776	$261.28	$261.30	$261.30
7 purchase totals =	$1,012.04		$1,114.3687	$1,114.37	$1,114.35	$1,114.50