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	$196.81	5.719%	$208.0656	$208.07	$208.05	$208.10
Purchase #2	$102.80	8.142%	$111.17	$111.17	$111.15	$111.20
Purchase #3	$122.88	6.336%	$130.6657	$130.67	$130.65	$130.70
Purchase #4	$175.47	9.524%	$192.1818	$192.18	$192.20	$192.20
Purchase #5	$96.83	3.435%	$100.1561	$100.16	$100.15	$100.20
Purchase #6	$125.56	8.617%	$136.3795	$136.38	$136.40	$136.40
Purchase #7	$103.32	6.220%	$109.7465	$109.75	$109.75	$109.70
7 purchase totals =	$923.67		$988.3652	$988.38	$988.35	$988.50