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	$9.65	4.744%	$10.1078	$10.11	$10.10	$10.10
Purchase #2	$50.64	6.137%	$53.7478	$53.75	$53.75	$53.70
Purchase #3	$76.90	8.519%	$83.4511	$83.45	$83.45	$83.50
Purchase #4	$96.40	8.848%	$104.9295	$104.93	$104.95	$104.90
Purchase #5	$50.29	6.384%	$53.5005	$53.50	$53.50	$53.50
Purchase #6	$125.61	13.755%	$142.8877	$142.89	$142.90	$142.90
Purchase #7	$14.35	10.431%	$15.8468	$15.85	$15.85	$15.80
7 purchase totals =	$423.84		$464.4712	$464.48	$464.50	$464.40