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	$49.57	9.677%	$54.3669	$54.37	$54.35	$54.40
Purchase #2	$9.29	12.435%	$10.4452	$10.45	$10.45	$10.40
Purchase #3	$225.69	8.767%	$245.4762	$245.48	$245.50	$245.50
Purchase #4	$164.31	12.575%	$184.972	$184.97	$184.95	$185.00
Purchase #5	$85.56	4.388%	$89.3144	$89.31	$89.30	$89.30
Purchase #6	$215.38	3.357%	$222.6103	$222.61	$222.60	$222.60
Purchase #7	$104.63	9.206%	$114.2622	$114.26	$114.25	$114.30
7 purchase totals =	$854.43		$921.4472	$921.45	$921.40	$921.50