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	$169.85	10.449%	$187.5976	$187.60	$187.60	$187.60
Purchase #2	$34.76	8.297%	$37.644	$37.64	$37.65	$37.60
Purchase #3	$206.48	4.678%	$216.1391	$216.14	$216.15	$216.10
Purchase #4	$30.49	6.819%	$32.5691	$32.57	$32.55	$32.60
Purchase #5	$88.55	13.714%	$100.6937	$100.69	$100.70	$100.70
Purchase #6	$180.75	5.368%	$190.4527	$190.45	$190.45	$190.50
Purchase #7	$193.89	3.473%	$200.6238	$200.62	$200.60	$200.60
7 purchase totals =	$904.77		$965.7200	$965.71	$965.70	$965.70