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	$245.55	6.533%	$261.5918	$261.59	$261.60	$261.60
Purchase #2	$62.87	5.702%	$66.4548	$66.45	$66.45	$66.50
Purchase #3	$64.82	11.369%	$72.1894	$72.19	$72.20	$72.20
Purchase #4	$54.55	13.333%	$61.8232	$61.82	$61.80	$61.80
Purchase #5	$213.93	4.442%	$223.4328	$223.43	$223.45	$223.40
Purchase #6	$89.85	4.360%	$93.7675	$93.77	$93.75	$93.80
Purchase #7	$77.43	11.690%	$86.4816	$86.48	$86.50	$86.50
7 purchase totals =	$809.00		$865.7411	$865.73	$865.75	$865.80