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	$62.72	3.740%	$65.0657	$65.07	$65.05	$65.10
Purchase #2	$250.41	8.551%	$271.8226	$271.82	$271.80	$271.80
Purchase #3	$9.57	4.622%	$10.0123	$10.01	$10.00	$10.00
Purchase #4	$90.31	4.376%	$94.262	$94.26	$94.25	$94.30
Purchase #5	$128.54	11.261%	$143.0149	$143.01	$143.00	$143.00
Purchase #6	$22.71	13.822%	$25.849	$25.85	$25.85	$25.80
Purchase #7	$42.99	8.278%	$46.5487	$46.55	$46.55	$46.50
7 purchase totals =	$607.25		$656.5752	$656.57	$656.50	$656.50