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	$33.32	6.785%	$35.5808	$35.58	$35.60	$35.60
Purchase #2	$10.65	4.245%	$11.1021	$11.10	$11.10	$11.10
Purchase #3	$182.37	7.605%	$196.2392	$196.24	$196.25	$196.20
Purchase #4	$62.38	8.811%	$67.8763	$67.88	$67.90	$67.90
Purchase #5	$215.94	12.110%	$242.0903	$242.09	$242.10	$242.10
Purchase #6	$138.67	9.144%	$151.35	$151.35	$151.35	$151.40
Purchase #7	$239.45	13.432%	$271.6129	$271.61	$271.60	$271.60
7 purchase totals =	$882.78		$975.8516	$975.85	$975.90	$975.90