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	$14.77	6.748%	$15.7667	$15.77	$15.75	$15.80
Purchase #2	$192.61	7.165%	$206.4105	$206.41	$206.40	$206.40
Purchase #3	$49.81	7.161%	$53.3769	$53.38	$53.40	$53.40
Purchase #4	$113.73	11.680%	$127.0137	$127.01	$127.00	$127.00
Purchase #5	$127.96	12.712%	$144.2263	$144.23	$144.25	$144.20
Purchase #6	$13.73	8.547%	$14.9035	$14.90	$14.90	$14.90
Purchase #7	$14.50	8.842%	$15.7821	$15.78	$15.80	$15.80
7 purchase totals =	$527.11		$577.4797	$577.48	$577.50	$577.50