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	$219.94	8.576%	$238.8021	$238.80	$238.80	$238.80
Purchase #2	$81.27	11.802%	$90.8615	$90.86	$90.85	$90.90
Purchase #3	$25.65	8.306%	$27.7805	$27.78	$27.80	$27.80
Purchase #4	$36.28	8.693%	$39.4338	$39.43	$39.45	$39.40
Purchase #5	$239.29	11.335%	$266.4135	$266.41	$266.40	$266.40
Purchase #6	$209.76	13.627%	$238.344	$238.34	$238.35	$238.30
Purchase #7	$139.65	5.557%	$147.4104	$147.41	$147.40	$147.40
7 purchase totals =	$951.84		$1,049.0458	$1,049.03	$1,049.05	$1,049.00