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	$99.89	9.361%	$109.2407	$109.24	$109.25	$109.20
Purchase #2	$138.38	7.719%	$149.0616	$149.06	$149.05	$149.10
Purchase #3	$35.82	4.322%	$37.3681	$37.37	$37.35	$37.40
Purchase #4	$108.45	3.487%	$112.2317	$112.23	$112.25	$112.20
Purchase #5	$20.46	10.403%	$22.5885	$22.59	$22.60	$22.60
Purchase #6	$103.96	9.264%	$113.5909	$113.59	$113.60	$113.60
Purchase #7	$204.88	5.490%	$216.1279	$216.13	$216.15	$216.10
7 purchase totals =	$711.84		$760.2094	$760.21	$760.25	$760.20