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	$179.55	11.670%	$200.5035	$200.50	$200.50	$200.50
Purchase #2	$240.74	13.583%	$273.4397	$273.44	$273.45	$273.40
Purchase #3	$15.47	13.209%	$17.5134	$17.51	$17.50	$17.50
Purchase #4	$203.77	3.555%	$211.014	$211.01	$211.00	$211.00
Purchase #5	$137.86	9.625%	$151.129	$151.13	$151.15	$151.10
Purchase #6	$102.56	5.741%	$108.448	$108.45	$108.45	$108.40
Purchase #7	$66.39	7.759%	$71.5412	$71.54	$71.55	$71.50
7 purchase totals =	$946.34		$1,033.5888	$1,033.58	$1,033.60	$1,033.40