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	$208.66	7.569%	$224.4535	$224.45	$224.45	$224.50
Purchase #2	$212.48	4.217%	$221.4403	$221.44	$221.45	$221.40
Purchase #3	$136.86	3.792%	$142.0497	$142.05	$142.05	$142.00
Purchase #4	$99.26	11.676%	$110.8496	$110.85	$110.85	$110.80
Purchase #5	$172.97	10.710%	$191.4951	$191.50	$191.50	$191.50
Purchase #6	$185.28	12.742%	$208.8884	$208.89	$208.90	$208.90
Purchase #7	$75.87	12.476%	$85.3355	$85.34	$85.35	$85.30
7 purchase totals =	$1,091.38		$1,184.5121	$1,184.52	$1,184.55	$1,184.40