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	$78.89	6.295%	$83.8561	$83.86	$83.85	$83.90
Purchase #2	$10.44	13.830%	$11.8839	$11.88	$11.90	$11.90
Purchase #3	$101.32	9.718%	$111.1663	$111.17	$111.15	$111.20
Purchase #4	$125.47	3.765%	$130.1939	$130.19	$130.20	$130.20
Purchase #5	$20.93	7.376%	$22.4738	$22.47	$22.45	$22.50
Purchase #6	$46.83	10.392%	$51.6966	$51.70	$51.70	$51.70
Purchase #7	$178.63	5.171%	$187.867	$187.87	$187.85	$187.90
7 purchase totals =	$562.51		$599.1376	$599.14	$599.10	$599.30