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	$31.55	7.717%	$33.9847	$33.98	$34.00	$34.00
Purchase #2	$146.77	8.256%	$158.8873	$158.89	$158.90	$158.90
Purchase #3	$202.28	12.244%	$227.0472	$227.05	$227.05	$227.00
Purchase #4	$109.46	9.334%	$119.677	$119.68	$119.70	$119.70
Purchase #5	$94.62	6.667%	$100.9283	$100.93	$100.95	$100.90
Purchase #6	$210.97	5.438%	$222.4425	$222.44	$222.45	$222.40
Purchase #7	$141.49	8.537%	$153.569	$153.57	$153.55	$153.60
7 purchase totals =	$937.14		$1,016.5360	$1,016.54	$1,016.60	$1,016.50