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	$64.48	10.661%	$71.3542	$71.35	$71.35	$71.40
Purchase #2	$248.51	12.801%	$280.3218	$280.32	$280.30	$280.30
Purchase #3	$36.90	13.281%	$41.8007	$41.80	$41.80	$41.80
Purchase #4	$90.44	4.725%	$94.7133	$94.71	$94.70	$94.70
Purchase #5	$91.30	8.721%	$99.2623	$99.26	$99.25	$99.30
Purchase #6	$113.68	8.621%	$123.4804	$123.48	$123.50	$123.50
Purchase #7	$59.56	13.695%	$67.7167	$67.72	$67.70	$67.70
7 purchase totals =	$704.87		$778.6494	$778.64	$778.60	$778.70