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	$222.98	3.792%	$231.4354	$231.44	$231.45	$231.40
Purchase #2	$210.32	5.389%	$221.6541	$221.65	$221.65	$221.70
Purchase #3	$57.29	9.706%	$62.8506	$62.85	$62.85	$62.90
Purchase #4	$228.33	4.155%	$237.8171	$237.82	$237.80	$237.80
Purchase #5	$203.89	5.148%	$214.3863	$214.39	$214.40	$214.40
Purchase #6	$60.99	10.540%	$67.4183	$67.42	$67.40	$67.40
Purchase #7	$13.29	12.148%	$14.9045	$14.90	$14.90	$14.90
7 purchase totals =	$997.09		$1,050.4663	$1,050.47	$1,050.45	$1,050.50