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	$225.34	7.568%	$242.3937	$242.39	$242.40	$242.40
Purchase #2	$169.44	13.154%	$191.7281	$191.73	$191.75	$191.70
Purchase #3	$95.71	8.556%	$103.8989	$103.90	$103.90	$103.90
Purchase #4	$94.29	11.437%	$105.0739	$105.07	$105.05	$105.10
Purchase #5	$219.78	3.126%	$226.6503	$226.65	$226.65	$226.70
Purchase #6	$118.28	5.590%	$124.8919	$124.89	$124.90	$124.90
Purchase #7	$35.96	13.813%	$40.9272	$40.93	$40.95	$40.90
7 purchase totals =	$958.80		$1,035.5640	$1,035.56	$1,035.60	$1,035.60