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	$209.64	6.431%	$223.1219	$223.12	$223.10	$223.10
Purchase #2	$94.80	10.585%	$104.8346	$104.83	$104.85	$104.80
Purchase #3	$227.86	12.600%	$256.5704	$256.57	$256.55	$256.60
Purchase #4	$19.29	7.716%	$20.7784	$20.78	$20.80	$20.80
Purchase #5	$90.90	10.252%	$100.2191	$100.22	$100.20	$100.20
Purchase #6	$121.30	10.510%	$134.0486	$134.05	$134.05	$134.00
Purchase #7	$32.49	8.380%	$35.2127	$35.21	$35.20	$35.20
7 purchase totals =	$796.28		$874.7857	$874.78	$874.75	$874.70