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	$43.81	5.247%	$46.1087	$46.11	$46.10	$46.10
Purchase #2	$155.87	13.410%	$176.7722	$176.77	$176.75	$176.80
Purchase #3	$179.33	9.787%	$196.881	$196.88	$196.90	$196.90
Purchase #4	$111.93	6.189%	$118.8573	$118.86	$118.85	$118.90
Purchase #5	$102.26	4.531%	$106.8934	$106.89	$106.90	$106.90
Purchase #6	$136.49	11.327%	$151.9502	$151.95	$151.95	$152.00
Purchase #7	$12.79	3.506%	$13.2384	$13.24	$13.25	$13.20
7 purchase totals =	$742.48		$810.7012	$810.70	$810.70	$810.80