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	$94.98	5.720%	$100.4129	$100.41	$100.40	$100.40
Purchase #2	$29.50	11.464%	$32.8819	$32.88	$32.90	$32.90
Purchase #3	$136.69	4.749%	$143.1814	$143.18	$143.20	$143.20
Purchase #4	$33.75	10.736%	$37.3734	$37.37	$37.35	$37.40
Purchase #5	$20.37	3.548%	$21.0927	$21.09	$21.10	$21.10
Purchase #6	$70.66	9.469%	$77.3508	$77.35	$77.35	$77.40
Purchase #7	$193.43	11.340%	$215.365	$215.37	$215.35	$215.40
7 purchase totals =	$579.38		$627.6581	$627.65	$627.65	$627.80