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	$234.65	3.289%	$242.3676	$242.37	$242.35	$242.40
Purchase #2	$152.40	9.574%	$166.9908	$166.99	$167.00	$167.00
Purchase #3	$92.82	8.217%	$100.447	$100.45	$100.45	$100.40
Purchase #4	$73.81	9.833%	$81.0677	$81.07	$81.05	$81.10
Purchase #5	$148.51	10.759%	$164.4882	$164.49	$164.50	$164.50
Purchase #6	$167.76	10.579%	$185.5073	$185.51	$185.50	$185.50
Purchase #7	$56.69	8.652%	$61.5948	$61.59	$61.60	$61.60
7 purchase totals =	$926.64		$1,002.4634	$1,002.47	$1,002.45	$1,002.50