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	$133.72	11.217%	$148.7194	$148.72	$148.70	$148.70
Purchase #2	$198.27	7.826%	$213.7866	$213.79	$213.80	$213.80
Purchase #3	$103.38	7.812%	$111.456	$111.46	$111.45	$111.50
Purchase #4	$238.82	4.660%	$249.949	$249.95	$249.95	$249.90
Purchase #5	$202.49	11.686%	$226.153	$226.15	$226.15	$226.20
Purchase #6	$234.75	6.463%	$249.9219	$249.92	$249.90	$249.90
Purchase #7	$57.96	7.724%	$62.4368	$62.44	$62.45	$62.40
7 purchase totals =	$1,169.39		$1,262.4227	$1,262.43	$1,262.40	$1,262.40