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	$82.50	4.844%	$86.4963	$86.50	$86.50	$86.50
Purchase #2	$167.75	10.619%	$185.5634	$185.56	$185.55	$185.60
Purchase #3	$171.60	3.863%	$178.2289	$178.23	$178.25	$178.20
Purchase #4	$220.40	13.681%	$250.5529	$250.55	$250.55	$250.60
Purchase #5	$105.54	11.175%	$117.3341	$117.33	$117.35	$117.30
Purchase #6	$184.40	8.487%	$200.05	$200.05	$200.05	$200.10
Purchase #7	$82.35	6.228%	$87.4788	$87.48	$87.50	$87.50
7 purchase totals =	$1,014.54		$1,105.7044	$1,105.70	$1,105.75	$1,105.80