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	$77.48	11.377%	$86.2949	$86.29	$86.30	$86.30
Purchase #2	$61.59	9.150%	$67.2255	$67.23	$67.25	$67.20
Purchase #3	$71.79	4.851%	$75.2725	$75.27	$75.25	$75.30
Purchase #4	$144.79	4.214%	$150.8915	$150.89	$150.90	$150.90
Purchase #5	$131.56	12.756%	$148.3418	$148.34	$148.35	$148.30
Purchase #6	$213.67	4.113%	$222.4582	$222.46	$222.45	$222.50
Purchase #7	$203.89	4.725%	$213.5238	$213.52	$213.50	$213.50
7 purchase totals =	$904.77		$964.0082	$964.00	$964.00	$964.00