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	$29.58	10.313%	$32.6306	$32.63	$32.65	$32.60
Purchase #2	$43.87	13.814%	$49.9302	$49.93	$49.95	$49.90
Purchase #3	$248.56	3.187%	$256.4816	$256.48	$256.50	$256.50
Purchase #4	$59.61	3.623%	$61.7697	$61.77	$61.75	$61.80
Purchase #5	$208.53	6.661%	$222.4202	$222.42	$222.40	$222.40
Purchase #6	$191.32	9.465%	$209.4284	$209.43	$209.45	$209.40
Purchase #7	$224.47	13.418%	$254.5894	$254.59	$254.60	$254.60
7 purchase totals =	$1,005.94		$1,087.2501	$1,087.25	$1,087.30	$1,087.20