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	$62.74	7.667%	$67.5503	$67.55	$67.55	$67.60
Purchase #2	$157.59	6.863%	$168.4054	$168.41	$168.40	$168.40
Purchase #3	$203.71	9.235%	$222.5226	$222.52	$222.50	$222.50
Purchase #4	$201.94	5.473%	$212.9922	$212.99	$213.00	$213.00
Purchase #5	$93.39	6.788%	$99.7293	$99.73	$99.75	$99.70
Purchase #6	$150.57	11.467%	$167.8359	$167.84	$167.85	$167.80
Purchase #7	$63.70	3.427%	$65.883	$65.88	$65.90	$65.90
7 purchase totals =	$933.64		$1,004.9187	$1,004.92	$1,004.95	$1,004.90