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	$220.79	11.380%	$245.9159	$245.92	$245.90	$245.90
Purchase #2	$85.61	5.249%	$90.1037	$90.10	$90.10	$90.10
Purchase #3	$52.81	11.840%	$59.0627	$59.06	$59.05	$59.10
Purchase #4	$53.31	5.157%	$56.0592	$56.06	$56.05	$56.10
Purchase #5	$106.67	6.845%	$113.9716	$113.97	$113.95	$114.00
Purchase #6	$141.62	9.676%	$155.3232	$155.32	$155.30	$155.30
Purchase #7	$109.26	9.319%	$119.4419	$119.44	$119.45	$119.40
7 purchase totals =	$770.07		$839.8782	$839.87	$839.80	$839.90