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	$223.44	12.301%	$250.9254	$250.93	$250.95	$250.90
Purchase #2	$7.61	12.556%	$8.5655	$8.57	$8.55	$8.60
Purchase #3	$90.97	12.790%	$102.6051	$102.61	$102.60	$102.60
Purchase #4	$99.75	4.763%	$104.5011	$104.50	$104.50	$104.50
Purchase #5	$171.91	7.764%	$185.2571	$185.26	$185.25	$185.30
Purchase #6	$46.90	10.682%	$51.9099	$51.91	$51.90	$51.90
Purchase #7	$219.42	11.838%	$245.3949	$245.39	$245.40	$245.40
7 purchase totals =	$860.00		$949.1590	$949.17	$949.15	$949.20