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	$33.48	12.281%	$37.5917	$37.59	$37.60	$37.60
Purchase #2	$97.37	9.728%	$106.8422	$106.84	$106.85	$106.80
Purchase #3	$137.77	7.442%	$148.0228	$148.02	$148.00	$148.00
Purchase #4	$69.88	9.429%	$76.469	$76.47	$76.45	$76.50
Purchase #5	$116.39	13.747%	$132.3901	$132.39	$132.40	$132.40
Purchase #6	$94.62	7.558%	$101.7714	$101.77	$101.75	$101.80
Purchase #7	$211.78	5.465%	$223.3538	$223.35	$223.35	$223.40
7 purchase totals =	$761.29		$826.4410	$826.43	$826.40	$826.50