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	$59.81	9.410%	$65.4381	$65.44	$65.45	$65.40
Purchase #2	$181.91	10.128%	$200.3338	$200.33	$200.35	$200.30
Purchase #3	$192.48	11.715%	$215.029	$215.03	$215.05	$215.00
Purchase #4	$91.89	7.250%	$98.552	$98.55	$98.55	$98.60
Purchase #5	$22.77	11.466%	$25.3808	$25.38	$25.40	$25.40
Purchase #6	$20.39	8.204%	$22.0628	$22.06	$22.05	$22.10
Purchase #7	$44.40	3.838%	$46.1041	$46.10	$46.10	$46.10
7 purchase totals =	$613.65		$672.9006	$672.89	$672.95	$672.90