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	$61.89	3.225%	$63.886	$63.89	$63.90	$63.90
Purchase #2	$87.55	13.739%	$99.5785	$99.58	$99.60	$99.60
Purchase #3	$18.45	10.469%	$20.3815	$20.38	$20.40	$20.40
Purchase #4	$249.96	12.835%	$282.0424	$282.04	$282.05	$282.00
Purchase #5	$30.86	9.801%	$33.8846	$33.88	$33.90	$33.90
Purchase #6	$124.42	10.707%	$137.7416	$137.74	$137.75	$137.70
Purchase #7	$168.81	4.118%	$175.7616	$175.76	$175.75	$175.80
7 purchase totals =	$741.94		$813.2762	$813.27	$813.35	$813.30