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	$123.59	13.628%	$140.4328	$140.43	$140.45	$140.40
Purchase #2	$250.56	9.656%	$274.7541	$274.75	$274.75	$274.80
Purchase #3	$119.91	6.324%	$127.4931	$127.49	$127.50	$127.50
Purchase #4	$242.84	12.234%	$272.549	$272.55	$272.55	$272.50
Purchase #5	$101.47	10.134%	$111.753	$111.75	$111.75	$111.80
Purchase #6	$43.86	12.788%	$49.4688	$49.47	$49.45	$49.50
Purchase #7	$43.68	6.355%	$46.4559	$46.46	$46.45	$46.50
7 purchase totals =	$925.91		$1,022.9067	$1,022.90	$1,022.90	$1,023.00