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	$30.58	9.754%	$33.5628	$33.56	$33.55	$33.60
Purchase #2	$17.42	11.784%	$19.4728	$19.47	$19.45	$19.50
Purchase #3	$143.78	5.644%	$151.8949	$151.89	$151.90	$151.90
Purchase #4	$64.25	10.551%	$71.029	$71.03	$71.05	$71.00
Purchase #5	$158.96	5.846%	$168.2528	$168.25	$168.25	$168.30
Purchase #6	$247.38	4.457%	$258.4057	$258.41	$258.40	$258.40
Purchase #7	$242.57	12.606%	$273.1484	$273.15	$273.15	$273.10
7 purchase totals =	$904.94		$975.7664	$975.76	$975.75	$975.80