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	$103.83	7.490%	$111.6069	$111.61	$111.60	$111.60
Purchase #2	$57.70	12.395%	$64.8519	$64.85	$64.85	$64.90
Purchase #3	$121.38	3.296%	$125.3807	$125.38	$125.40	$125.40
Purchase #4	$214.48	5.294%	$225.8346	$225.83	$225.85	$225.80
Purchase #5	$201.76	8.265%	$218.4355	$218.44	$218.45	$218.40
Purchase #6	$189.86	8.316%	$205.6488	$205.65	$205.65	$205.60
Purchase #7	$119.62	12.235%	$134.2555	$134.26	$134.25	$134.30
7 purchase totals =	$1,008.63		$1,086.0139	$1,086.02	$1,086.05	$1,086.00