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	$87.79	5.230%	$92.3814	$92.38	$92.40	$92.40
Purchase #2	$61.51	13.342%	$69.7167	$69.72	$69.70	$69.70
Purchase #3	$242.85	3.167%	$250.5411	$250.54	$250.55	$250.50
Purchase #4	$148.93	4.800%	$156.0786	$156.08	$156.10	$156.10
Purchase #5	$219.74	9.536%	$240.6944	$240.69	$240.70	$240.70
Purchase #6	$192.29	13.804%	$218.8337	$218.83	$218.85	$218.80
Purchase #7	$54.38	9.533%	$59.564	$59.56	$59.55	$59.60
7 purchase totals =	$1,007.49		$1,087.8099	$1,087.80	$1,087.85	$1,087.80