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	$48.56	10.299%	$53.5612	$53.56	$53.55	$53.60
Purchase #2	$184.33	3.563%	$190.8977	$190.90	$190.90	$190.90
Purchase #3	$71.93	7.223%	$77.1255	$77.13	$77.15	$77.10
Purchase #4	$53.30	8.583%	$57.8747	$57.87	$57.85	$57.90
Purchase #5	$101.70	9.329%	$111.1876	$111.19	$111.20	$111.20
Purchase #6	$225.74	10.537%	$249.5262	$249.53	$249.55	$249.50
Purchase #7	$162.68	8.481%	$176.4769	$176.48	$176.50	$176.50
7 purchase totals =	$848.24		$916.6498	$916.66	$916.70	$916.70