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	$23.45	3.505%	$24.2719	$24.27	$24.25	$24.30
Purchase #2	$16.32	12.287%	$18.3252	$18.33	$18.35	$18.30
Purchase #3	$54.62	12.858%	$61.643	$61.64	$61.65	$61.60
Purchase #4	$152.93	7.546%	$164.4701	$164.47	$164.45	$164.50
Purchase #5	$94.31	11.348%	$105.0123	$105.01	$105.00	$105.00
Purchase #6	$246.59	4.407%	$257.4572	$257.46	$257.45	$257.50
Purchase #7	$76.91	7.151%	$82.4098	$82.41	$82.40	$82.40
7 purchase totals =	$665.13		$713.5895	$713.59	$713.55	$713.60