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	$53.57	8.236%	$57.982	$57.98	$58.00	$58.00
Purchase #2	$166.86	12.299%	$187.3821	$187.38	$187.40	$187.40
Purchase #3	$142.79	10.762%	$158.1571	$158.16	$158.15	$158.20
Purchase #4	$56.86	4.574%	$59.4608	$59.46	$59.45	$59.50
Purchase #5	$46.50	8.409%	$50.4102	$50.41	$50.40	$50.40
Purchase #6	$164.90	5.210%	$173.4913	$173.49	$173.50	$173.50
Purchase #7	$92.39	8.585%	$100.3217	$100.32	$100.30	$100.30
7 purchase totals =	$723.87		$787.2052	$787.20	$787.20	$787.30