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	$102.54	3.217%	$105.8387	$105.84	$105.85	$105.80
Purchase #2	$53.94	12.729%	$60.806	$60.81	$60.80	$60.80
Purchase #3	$32.43	7.388%	$34.8259	$34.83	$34.85	$34.80
Purchase #4	$25.96	11.750%	$29.0103	$29.01	$29.00	$29.00
Purchase #5	$36.38	11.171%	$40.444	$40.44	$40.45	$40.40
Purchase #6	$86.41	8.651%	$93.8853	$93.89	$93.90	$93.90
Purchase #7	$58.42	5.872%	$61.8504	$61.85	$61.85	$61.90
7 purchase totals =	$396.08		$426.6606	$426.67	$426.70	$426.60