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	$122.61	7.105%	$131.3214	$131.32	$131.30	$131.30
Purchase #2	$51.76	5.496%	$54.6047	$54.60	$54.60	$54.60
Purchase #3	$57.34	6.584%	$61.1153	$61.12	$61.10	$61.10
Purchase #4	$218.79	5.749%	$231.3682	$231.37	$231.35	$231.40
Purchase #5	$168.29	7.366%	$180.6862	$180.69	$180.70	$180.70
Purchase #6	$107.58	10.659%	$119.047	$119.05	$119.05	$119.00
Purchase #7	$139.45	13.732%	$158.5993	$158.60	$158.60	$158.60
7 purchase totals =	$865.82		$936.7421	$936.75	$936.70	$936.70