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	$132.37	12.434%	$148.8289	$148.83	$148.85	$148.80
Purchase #2	$193.29	3.487%	$200.03	$200.03	$200.05	$200.00
Purchase #3	$129.85	10.554%	$143.5544	$143.55	$143.55	$143.60
Purchase #4	$224.37	7.424%	$241.0272	$241.03	$241.05	$241.00
Purchase #5	$28.58	13.533%	$32.4477	$32.45	$32.45	$32.40
Purchase #6	$169.91	9.390%	$185.8645	$185.86	$185.85	$185.90
Purchase #7	$131.86	5.824%	$139.5395	$139.54	$139.55	$139.50
7 purchase totals =	$1,010.23		$1,091.2922	$1,091.29	$1,091.35	$1,091.20