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	$56.48	5.600%	$59.6429	$59.64	$59.65	$59.60
Purchase #2	$25.73	12.621%	$28.9774	$28.98	$29.00	$29.00
Purchase #3	$29.46	6.811%	$31.4665	$31.47	$31.45	$31.50
Purchase #4	$194.95	7.133%	$208.8558	$208.86	$208.85	$208.90
Purchase #5	$242.61	5.257%	$255.364	$255.36	$255.35	$255.40
Purchase #6	$119.47	3.217%	$123.3133	$123.31	$123.30	$123.30
Purchase #7	$156.50	4.523%	$163.5785	$163.58	$163.60	$163.60
7 purchase totals =	$825.20		$871.1984	$871.20	$871.20	$871.30