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	$205.89	6.810%	$219.9111	$219.91	$219.90	$219.90
Purchase #2	$103.80	10.695%	$114.9014	$114.90	$114.90	$114.90
Purchase #3	$202.49	6.770%	$216.1986	$216.20	$216.20	$216.20
Purchase #4	$222.38	6.769%	$237.4329	$237.43	$237.45	$237.40
Purchase #5	$115.47	7.335%	$123.9397	$123.94	$123.95	$123.90
Purchase #6	$140.50	3.206%	$145.0044	$145.00	$145.00	$145.00
Purchase #7	$40.33	6.243%	$42.8478	$42.85	$42.85	$42.80
7 purchase totals =	$1,030.86		$1,100.2359	$1,100.23	$1,100.25	$1,100.10