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	$104.87	7.544%	$112.7814	$112.78	$112.80	$112.80
Purchase #2	$127.50	13.575%	$144.8081	$144.81	$144.80	$144.80
Purchase #3	$152.53	6.581%	$162.568	$162.57	$162.55	$162.60
Purchase #4	$140.77	11.822%	$157.4118	$157.41	$157.40	$157.40
Purchase #5	$164.98	13.439%	$187.1517	$187.15	$187.15	$187.20
Purchase #6	$28.35	11.321%	$31.5595	$31.56	$31.55	$31.60
Purchase #7	$10.51	6.608%	$11.2045	$11.20	$11.20	$11.20
7 purchase totals =	$729.51		$807.4850	$807.48	$807.45	$807.60