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	$141.66	10.855%	$157.0372	$157.04	$157.05	$157.00
Purchase #2	$102.34	8.679%	$111.2221	$111.22	$111.20	$111.20
Purchase #3	$43.27	6.606%	$46.1284	$46.13	$46.15	$46.10
Purchase #4	$56.92	4.273%	$59.3522	$59.35	$59.35	$59.40
Purchase #5	$103.84	7.155%	$111.2698	$111.27	$111.25	$111.30
Purchase #6	$7.83	13.491%	$8.8863	$8.89	$8.90	$8.90
Purchase #7	$135.55	3.297%	$140.0191	$140.02	$140.00	$140.00
7 purchase totals =	$591.41		$633.9151	$633.92	$633.90	$633.90