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	$78.37	4.713%	$82.0636	$82.06	$82.05	$82.10
Purchase #2	$193.34	13.746%	$219.9165	$219.92	$219.90	$219.90
Purchase #3	$151.36	13.203%	$171.3441	$171.34	$171.35	$171.30
Purchase #4	$66.49	4.625%	$69.5652	$69.57	$69.55	$69.60
Purchase #5	$17.94	5.145%	$18.863	$18.86	$18.85	$18.90
Purchase #6	$42.42	8.114%	$45.862	$45.86	$45.85	$45.90
Purchase #7	$50.89	10.410%	$56.1876	$56.19	$56.20	$56.20
7 purchase totals =	$600.81		$663.8020	$663.80	$663.75	$663.90