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	$193.33	7.822%	$208.4523	$208.45	$208.45	$208.50
Purchase #2	$202.46	8.708%	$220.0902	$220.09	$220.10	$220.10
Purchase #3	$99.97	11.128%	$111.0947	$111.09	$111.10	$111.10
Purchase #4	$49.44	3.424%	$51.1328	$51.13	$51.15	$51.10
Purchase #5	$41.74	4.761%	$43.7272	$43.73	$43.75	$43.70
Purchase #6	$72.64	6.705%	$77.5105	$77.51	$77.50	$77.50
Purchase #7	$87.67	3.177%	$90.4553	$90.46	$90.45	$90.50
7 purchase totals =	$747.25		$802.4630	$802.46	$802.50	$802.50