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	$63.84	5.336%	$67.2465	$67.25	$67.25	$67.20
Purchase #2	$151.30	13.493%	$171.7149	$171.71	$171.70	$171.70
Purchase #3	$218.85	12.734%	$246.7184	$246.72	$246.70	$246.70
Purchase #4	$176.34	4.626%	$184.4975	$184.50	$184.50	$184.50
Purchase #5	$35.62	6.677%	$37.9983	$38.00	$38.00	$38.00
Purchase #6	$52.27	3.663%	$54.1847	$54.18	$54.20	$54.20
Purchase #7	$239.53	6.258%	$254.5198	$254.52	$254.50	$254.50
7 purchase totals =	$937.75		$1,016.8801	$1,016.88	$1,016.85	$1,016.80