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	$151.88	10.869%	$168.3878	$168.39	$168.40	$168.40
Purchase #2	$102.57	3.381%	$106.0379	$106.04	$106.05	$106.00
Purchase #3	$33.26	10.410%	$36.7224	$36.72	$36.70	$36.70
Purchase #4	$171.41	7.665%	$184.5486	$184.55	$184.55	$184.50
Purchase #5	$111.40	8.509%	$120.879	$120.88	$120.90	$120.90
Purchase #6	$45.37	11.383%	$50.5345	$50.53	$50.55	$50.50
Purchase #7	$58.69	4.750%	$61.4778	$61.48	$61.50	$61.50
7 purchase totals =	$674.58		$728.5880	$728.59	$728.65	$728.50