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	$203.89	6.365%	$216.8676	$216.87	$216.85	$216.90
Purchase #2	$108.41	12.158%	$121.5905	$121.59	$121.60	$121.60
Purchase #3	$11.31	7.582%	$12.1675	$12.17	$12.15	$12.20
Purchase #4	$239.49	9.108%	$261.3027	$261.30	$261.30	$261.30
Purchase #5	$216.30	8.252%	$234.1491	$234.15	$234.15	$234.10
Purchase #6	$21.56	11.398%	$24.0174	$24.02	$24.00	$24.00
Purchase #7	$177.64	7.810%	$191.5137	$191.51	$191.50	$191.50
7 purchase totals =	$978.60		$1,061.6085	$1,061.61	$1,061.55	$1,061.60