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	$66.35	10.596%	$73.3804	$73.38	$73.40	$73.40
Purchase #2	$138.76	12.863%	$156.6087	$156.61	$156.60	$156.60
Purchase #3	$7.48	3.592%	$7.7487	$7.75	$7.75	$7.70
Purchase #4	$131.54	5.374%	$138.609	$138.61	$138.60	$138.60
Purchase #5	$21.90	7.810%	$23.6104	$23.61	$23.60	$23.60
Purchase #6	$214.25	5.434%	$225.8923	$225.89	$225.90	$225.90
Purchase #7	$119.86	6.738%	$127.9362	$127.94	$127.95	$127.90
7 purchase totals =	$700.14		$753.7857	$753.79	$753.80	$753.70