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	$216.27	12.543%	$243.3967	$243.40	$243.40	$243.40
Purchase #2	$83.71	6.379%	$89.0499	$89.05	$89.05	$89.00
Purchase #3	$213.57	6.137%	$226.6768	$226.68	$226.70	$226.70
Purchase #4	$131.35	10.757%	$145.4793	$145.48	$145.50	$145.50
Purchase #5	$92.46	7.705%	$99.584	$99.58	$99.60	$99.60
Purchase #6	$40.72	9.138%	$44.441	$44.44	$44.45	$44.40
Purchase #7	$201.57	3.571%	$208.7681	$208.77	$208.75	$208.80
7 purchase totals =	$979.65		$1,057.3958	$1,057.40	$1,057.45	$1,057.40