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	$117.47	4.705%	$122.997	$123.00	$123.00	$123.00
Purchase #2	$70.72	11.579%	$78.9087	$78.91	$78.90	$78.90
Purchase #3	$135.92	5.158%	$142.9308	$142.93	$142.95	$142.90
Purchase #4	$158.31	5.146%	$166.4566	$166.46	$166.45	$166.50
Purchase #5	$21.38	9.558%	$23.4235	$23.42	$23.40	$23.40
Purchase #6	$219.83	11.690%	$245.5281	$245.53	$245.55	$245.50
Purchase #7	$199.51	4.386%	$208.2605	$208.26	$208.25	$208.30
7 purchase totals =	$923.14		$988.5052	$988.51	$988.50	$988.50