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	$133.32	11.431%	$148.5598	$148.56	$148.55	$148.60
Purchase #2	$11.74	5.245%	$12.3558	$12.36	$12.35	$12.40
Purchase #3	$197.93	10.503%	$218.7186	$218.72	$218.70	$218.70
Purchase #4	$117.26	5.357%	$123.5416	$123.54	$123.55	$123.50
Purchase #5	$212.98	4.603%	$222.7835	$222.78	$222.80	$222.80
Purchase #6	$22.88	9.619%	$25.0808	$25.08	$25.10	$25.10
Purchase #7	$72.52	8.159%	$78.4369	$78.44	$78.45	$78.40
7 purchase totals =	$768.63		$829.4770	$829.48	$829.50	$829.50