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	$109.33	9.207%	$119.396	$119.40	$119.40	$119.40
Purchase #2	$83.28	5.652%	$87.987	$87.99	$88.00	$88.00
Purchase #3	$43.85	3.671%	$45.4597	$45.46	$45.45	$45.50
Purchase #4	$44.54	5.421%	$46.9545	$46.95	$46.95	$47.00
Purchase #5	$53.46	10.583%	$59.1177	$59.12	$59.10	$59.10
Purchase #6	$35.90	13.708%	$40.8212	$40.82	$40.80	$40.80
Purchase #7	$43.51	10.514%	$48.0846	$48.08	$48.10	$48.10
7 purchase totals =	$413.87		$447.8207	$447.82	$447.80	$447.90