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	$175.38	7.162%	$187.9407	$187.94	$187.95	$187.90
Purchase #2	$162.71	8.537%	$176.6006	$176.60	$176.60	$176.60
Purchase #3	$186.44	9.462%	$204.081	$204.08	$204.10	$204.10
Purchase #4	$151.79	11.123%	$168.6736	$168.67	$168.65	$168.70
Purchase #5	$93.61	6.263%	$99.4728	$99.47	$99.45	$99.50
Purchase #6	$100.45	12.826%	$113.3337	$113.33	$113.35	$113.30
Purchase #7	$76.27	12.606%	$85.8846	$85.88	$85.90	$85.90
7 purchase totals =	$946.65		$1,035.9870	$1,035.97	$1,036.00	$1,036.00