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	$35.75	3.129%	$36.8686	$36.87	$36.85	$36.90
Purchase #2	$17.60	11.293%	$19.5876	$19.59	$19.60	$19.60
Purchase #3	$145.89	5.104%	$153.3362	$153.34	$153.35	$153.30
Purchase #4	$94.34	9.753%	$103.541	$103.54	$103.55	$103.50
Purchase #5	$35.44	6.742%	$37.8294	$37.83	$37.85	$37.80
Purchase #6	$21.98	4.128%	$22.8873	$22.89	$22.90	$22.90
Purchase #7	$11.85	5.438%	$12.4944	$12.49	$12.50	$12.50
7 purchase totals =	$362.85		$386.5445	$386.55	$386.60	$386.50