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	$143.79	8.791%	$156.4306	$156.43	$156.45	$156.40
Purchase #2	$185.43	7.420%	$199.1889	$199.19	$199.20	$199.20
Purchase #3	$125.95	8.809%	$137.0449	$137.04	$137.05	$137.00
Purchase #4	$56.90	5.321%	$59.9276	$59.93	$59.95	$59.90
Purchase #5	$119.36	3.132%	$123.0984	$123.10	$123.10	$123.10
Purchase #6	$208.28	13.780%	$236.981	$236.98	$237.00	$237.00
Purchase #7	$88.87	13.400%	$100.7786	$100.78	$100.80	$100.80
7 purchase totals =	$928.58		$1,013.4500	$1,013.45	$1,013.55	$1,013.40