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	$241.32	11.222%	$268.4009	$268.40	$268.40	$268.40
Purchase #2	$85.44	11.592%	$95.3442	$95.34	$95.35	$95.30
Purchase #3	$126.81	4.509%	$132.5279	$132.53	$132.55	$132.50
Purchase #4	$57.83	3.646%	$59.9385	$59.94	$59.95	$59.90
Purchase #5	$190.80	13.616%	$216.7793	$216.78	$216.80	$216.80
Purchase #6	$61.90	9.872%	$68.0108	$68.01	$68.00	$68.00
Purchase #7	$123.44	6.252%	$131.1575	$131.16	$131.15	$131.20
7 purchase totals =	$887.54		$972.1591	$972.16	$972.20	$972.10