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	$114.66	7.467%	$123.2217	$123.22	$123.20	$123.20
Purchase #2	$129.58	10.681%	$143.4204	$143.42	$143.40	$143.40
Purchase #3	$37.25	7.152%	$39.9141	$39.91	$39.90	$39.90
Purchase #4	$107.84	11.190%	$119.9073	$119.91	$119.90	$119.90
Purchase #5	$48.72	7.275%	$52.2644	$52.26	$52.25	$52.30
Purchase #6	$77.68	5.749%	$82.1458	$82.15	$82.15	$82.10
Purchase #7	$42.89	3.471%	$44.3787	$44.38	$44.40	$44.40
7 purchase totals =	$558.62		$605.2524	$605.25	$605.20	$605.20