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	$187.83	8.549%	$203.8876	$203.89	$203.90	$203.90
Purchase #2	$200.96	12.213%	$225.5032	$225.50	$225.50	$225.50
Purchase #3	$77.32	7.208%	$82.8932	$82.89	$82.90	$82.90
Purchase #4	$14.97	5.637%	$15.8139	$15.81	$15.80	$15.80
Purchase #5	$178.87	7.145%	$191.6503	$191.65	$191.65	$191.70
Purchase #6	$241.36	13.571%	$274.115	$274.12	$274.10	$274.10
Purchase #7	$67.61	6.761%	$72.1811	$72.18	$72.20	$72.20
7 purchase totals =	$968.92		$1,066.0443	$1,066.04	$1,066.05	$1,066.10