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	$203.48	9.382%	$222.5705	$222.57	$222.55	$222.60
Purchase #2	$50.51	9.510%	$55.3135	$55.31	$55.30	$55.30
Purchase #3	$13.60	3.691%	$14.102	$14.10	$14.10	$14.10
Purchase #4	$109.67	12.725%	$123.6255	$123.63	$123.65	$123.60
Purchase #5	$180.69	6.703%	$192.8017	$192.80	$192.80	$192.80
Purchase #6	$160.72	13.196%	$181.9286	$181.93	$181.95	$181.90
Purchase #7	$186.89	12.185%	$209.6625	$209.66	$209.65	$209.70
7 purchase totals =	$905.56		$1,000.0043	$1,000.00	$1,000.00	$1,000.00