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	$246.41	8.709%	$267.8698	$267.87	$267.85	$267.90
Purchase #2	$239.34	9.508%	$262.0964	$262.10	$262.10	$262.10
Purchase #3	$19.44	12.726%	$21.9139	$21.91	$21.90	$21.90
Purchase #4	$217.56	5.192%	$228.8557	$228.86	$228.85	$228.90
Purchase #5	$92.66	12.854%	$104.5705	$104.57	$104.55	$104.60
Purchase #6	$67.45	6.341%	$71.727	$71.73	$71.75	$71.70
Purchase #7	$104.45	6.328%	$111.0596	$111.06	$111.05	$111.10
7 purchase totals =	$987.31		$1,068.0929	$1,068.10	$1,068.05	$1,068.20