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	$64.29	11.365%	$71.5966	$71.60	$71.60	$71.60
Purchase #2	$237.38	10.729%	$262.8485	$262.85	$262.85	$262.80
Purchase #3	$11.42	13.157%	$12.9225	$12.92	$12.90	$12.90
Purchase #4	$195.71	13.676%	$222.4753	$222.48	$222.50	$222.50
Purchase #5	$103.99	10.212%	$114.6095	$114.61	$114.60	$114.60
Purchase #6	$97.96	4.754%	$102.617	$102.62	$102.60	$102.60
Purchase #7	$64.44	4.266%	$67.189	$67.19	$67.20	$67.20
7 purchase totals =	$775.19		$854.2584	$854.27	$854.25	$854.20