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	$46.57	9.780%	$51.1245	$51.12	$51.10	$51.10
Purchase #2	$129.89	3.839%	$134.8765	$134.88	$134.90	$134.90
Purchase #3	$44.68	13.825%	$50.857	$50.86	$50.85	$50.90
Purchase #4	$12.54	10.484%	$13.8547	$13.85	$13.85	$13.90
Purchase #5	$117.95	7.622%	$126.9401	$126.94	$126.95	$126.90
Purchase #6	$14.89	10.799%	$16.498	$16.50	$16.50	$16.50
Purchase #7	$77.31	6.122%	$82.0429	$82.04	$82.05	$82.00
7 purchase totals =	$443.83		$476.1937	$476.19	$476.20	$476.20