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	$200.81	13.462%	$227.843	$227.84	$227.85	$227.80
Purchase #2	$57.29	3.335%	$59.2006	$59.20	$59.20	$59.20
Purchase #3	$170.92	10.240%	$188.4222	$188.42	$188.40	$188.40
Purchase #4	$228.29	7.307%	$244.9712	$244.97	$244.95	$245.00
Purchase #5	$59.26	8.838%	$64.4974	$64.50	$64.50	$64.50
Purchase #6	$242.51	5.297%	$255.3558	$255.36	$255.35	$255.40
Purchase #7	$211.90	13.197%	$239.8644	$239.86	$239.85	$239.90
7 purchase totals =	$1,170.98		$1,280.1546	$1,280.15	$1,280.10	$1,280.20