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	$111.92	11.727%	$125.0449	$125.04	$125.05	$125.00
Purchase #2	$233.47	9.598%	$255.8785	$255.88	$255.90	$255.90
Purchase #3	$223.37	4.683%	$233.8304	$233.83	$233.85	$233.80
Purchase #4	$62.51	8.457%	$67.7965	$67.80	$67.80	$67.80
Purchase #5	$138.79	13.482%	$157.5017	$157.50	$157.50	$157.50
Purchase #6	$100.98	12.294%	$113.3945	$113.39	$113.40	$113.40
Purchase #7	$114.97	7.175%	$123.2191	$123.22	$123.20	$123.20
7 purchase totals =	$986.01		$1,076.6656	$1,076.66	$1,076.70	$1,076.60