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	$172.79	13.201%	$195.6	$195.60	$195.60	$195.60
Purchase #2	$216.60	13.575%	$246.0035	$246.00	$246.00	$246.00
Purchase #3	$136.41	11.786%	$152.4873	$152.49	$152.50	$152.50
Purchase #4	$49.81	5.204%	$52.4021	$52.40	$52.40	$52.40
Purchase #5	$98.34	11.719%	$109.8645	$109.86	$109.85	$109.90
Purchase #6	$17.85	8.105%	$19.2967	$19.30	$19.30	$19.30
Purchase #7	$54.52	8.322%	$59.0572	$59.06	$59.05	$59.10
7 purchase totals =	$746.32		$834.7113	$834.71	$834.70	$834.80