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	$206.35	4.803%	$216.261	$216.26	$216.25	$216.30
Purchase #2	$147.33	3.264%	$152.1389	$152.14	$152.15	$152.10
Purchase #3	$35.43	13.660%	$40.2697	$40.27	$40.25	$40.30
Purchase #4	$105.45	5.738%	$111.5007	$111.50	$111.50	$111.50
Purchase #5	$205.25	5.833%	$217.2222	$217.22	$217.20	$217.20
Purchase #6	$96.37	13.602%	$109.4782	$109.48	$109.50	$109.50
Purchase #7	$132.48	13.614%	$150.5158	$150.52	$150.50	$150.50
7 purchase totals =	$928.66		$997.3865	$997.39	$997.35	$997.40