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	$196.76	10.667%	$217.7484	$217.75	$217.75	$217.70
Purchase #2	$192.87	3.250%	$199.1383	$199.14	$199.15	$199.10
Purchase #3	$230.44	8.479%	$249.979	$249.98	$250.00	$250.00
Purchase #4	$220.78	4.797%	$231.3708	$231.37	$231.35	$231.40
Purchase #5	$35.28	11.742%	$39.4226	$39.42	$39.40	$39.40
Purchase #6	$74.78	7.410%	$80.3212	$80.32	$80.30	$80.30
Purchase #7	$176.61	8.492%	$191.6077	$191.61	$191.60	$191.60
7 purchase totals =	$1,127.52		$1,209.5880	$1,209.59	$1,209.55	$1,209.50