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	$213.43	10.359%	$235.5392	$235.54	$235.55	$235.50
Purchase #2	$17.35	12.684%	$19.5507	$19.55	$19.55	$19.60
Purchase #3	$29.87	5.145%	$31.4068	$31.41	$31.40	$31.40
Purchase #4	$86.62	4.376%	$90.4105	$90.41	$90.40	$90.40
Purchase #5	$92.28	7.665%	$99.3533	$99.35	$99.35	$99.40
Purchase #6	$45.99	10.613%	$50.8709	$50.87	$50.85	$50.90
Purchase #7	$131.61	11.731%	$147.0492	$147.05	$147.05	$147.00
7 purchase totals =	$617.15		$674.1806	$674.18	$674.15	$674.20