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	$191.61	6.349%	$203.7753	$203.78	$203.80	$203.80
Purchase #2	$35.82	3.484%	$37.068	$37.07	$37.05	$37.10
Purchase #3	$245.75	4.791%	$257.5239	$257.52	$257.50	$257.50
Purchase #4	$52.76	11.815%	$58.9936	$58.99	$59.00	$59.00
Purchase #5	$156.94	3.627%	$162.6322	$162.63	$162.65	$162.60
Purchase #6	$80.37	10.214%	$88.579	$88.58	$88.60	$88.60
Purchase #7	$88.25	13.151%	$99.8558	$99.86	$99.85	$99.90
7 purchase totals =	$851.50		$908.4278	$908.43	$908.45	$908.50