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	$193.26	6.477%	$205.7775	$205.78	$205.80	$205.80
Purchase #2	$177.76	5.617%	$187.7448	$187.74	$187.75	$187.70
Purchase #3	$59.89	3.288%	$61.8592	$61.86	$61.85	$61.90
Purchase #4	$21.83	11.737%	$24.3922	$24.39	$24.40	$24.40
Purchase #5	$137.38	9.316%	$150.1783	$150.18	$150.20	$150.20
Purchase #6	$156.90	7.648%	$168.8997	$168.90	$168.90	$168.90
Purchase #7	$46.46	5.373%	$48.9563	$48.96	$48.95	$49.00
7 purchase totals =	$793.48		$847.8080	$847.81	$847.85	$847.90