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	$160.41	5.625%	$169.4331	$169.43	$169.45	$169.40
Purchase #2	$116.78	6.218%	$124.0414	$124.04	$124.05	$124.00
Purchase #3	$89.56	4.807%	$93.8651	$93.87	$93.85	$93.90
Purchase #4	$89.27	3.713%	$92.5846	$92.58	$92.60	$92.60
Purchase #5	$97.35	8.828%	$105.9441	$105.94	$105.95	$105.90
Purchase #6	$34.43	7.654%	$37.0653	$37.07	$37.05	$37.10
Purchase #7	$57.46	9.354%	$62.8348	$62.83	$62.85	$62.80
7 purchase totals =	$645.26		$685.7684	$685.76	$685.80	$685.70