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	$84.85	12.691%	$95.6183	$95.62	$95.60	$95.60
Purchase #2	$164.64	3.383%	$170.2098	$170.21	$170.20	$170.20
Purchase #3	$148.28	9.289%	$162.0537	$162.05	$162.05	$162.10
Purchase #4	$43.66	3.833%	$45.3335	$45.33	$45.35	$45.30
Purchase #5	$195.64	13.782%	$222.6031	$222.60	$222.60	$222.60
Purchase #6	$145.51	4.839%	$152.5512	$152.55	$152.55	$152.60
Purchase #7	$118.85	13.490%	$134.8829	$134.88	$134.90	$134.90
7 purchase totals =	$901.43		$983.2525	$983.24	$983.25	$983.30