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	$148.55	10.540%	$164.2072	$164.21	$164.20	$164.20
Purchase #2	$52.92	11.843%	$59.1873	$59.19	$59.20	$59.20
Purchase #3	$119.91	9.531%	$131.3386	$131.34	$131.35	$131.30
Purchase #4	$70.27	9.308%	$76.8107	$76.81	$76.80	$76.80
Purchase #5	$131.55	8.599%	$142.862	$142.86	$142.85	$142.90
Purchase #6	$133.47	4.179%	$139.0477	$139.05	$139.05	$139.00
Purchase #7	$207.89	3.569%	$215.3096	$215.31	$215.30	$215.30
7 purchase totals =	$864.56		$928.7631	$928.77	$928.75	$928.70