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	$200.92	5.699%	$212.3704	$212.37	$212.35	$212.40
Purchase #2	$171.86	3.461%	$177.8081	$177.81	$177.80	$177.80
Purchase #3	$86.83	7.422%	$93.2745	$93.27	$93.25	$93.30
Purchase #4	$45.27	6.314%	$48.1283	$48.13	$48.15	$48.10
Purchase #5	$103.93	8.653%	$112.9231	$112.92	$112.90	$112.90
Purchase #6	$179.83	9.282%	$196.5218	$196.52	$196.50	$196.50
Purchase #7	$96.26	6.266%	$102.2917	$102.29	$102.30	$102.30
7 purchase totals =	$884.90		$943.3179	$943.31	$943.25	$943.30