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	$202.81	11.295%	$225.7174	$225.72	$225.70	$225.70
Purchase #2	$131.82	6.807%	$140.793	$140.79	$140.80	$140.80
Purchase #3	$22.52	6.854%	$24.0635	$24.06	$24.05	$24.10
Purchase #4	$113.26	10.296%	$124.9212	$124.92	$124.90	$124.90
Purchase #5	$82.31	3.383%	$85.0945	$85.09	$85.10	$85.10
Purchase #6	$37.53	3.744%	$38.9351	$38.94	$38.95	$38.90
Purchase #7	$142.98	9.758%	$156.932	$156.93	$156.95	$156.90
7 purchase totals =	$733.23		$796.4567	$796.45	$796.45	$796.40