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	$31.32	13.571%	$35.5704	$35.57	$35.55	$35.60
Purchase #2	$180.96	7.294%	$194.1592	$194.16	$194.15	$194.20
Purchase #3	$12.76	5.263%	$13.4316	$13.43	$13.45	$13.40
Purchase #4	$25.38	7.362%	$27.2485	$27.25	$27.25	$27.20
Purchase #5	$100.69	11.830%	$112.6016	$112.60	$112.60	$112.60
Purchase #6	$62.79	12.226%	$70.4667	$70.47	$70.45	$70.50
Purchase #7	$132.94	13.254%	$150.5599	$150.56	$150.55	$150.60
7 purchase totals =	$546.84		$604.0379	$604.04	$604.00	$604.10