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	$38.49	11.427%	$42.8883	$42.89	$42.90	$42.90
Purchase #2	$106.92	10.334%	$117.9691	$117.97	$117.95	$118.00
Purchase #3	$150.75	11.264%	$167.7305	$167.73	$167.75	$167.70
Purchase #4	$208.92	9.495%	$228.757	$228.76	$228.75	$228.80
Purchase #5	$42.57	6.650%	$45.4009	$45.40	$45.40	$45.40
Purchase #6	$168.77	12.849%	$190.4553	$190.46	$190.45	$190.50
Purchase #7	$136.32	12.460%	$153.3055	$153.31	$153.30	$153.30
7 purchase totals =	$852.74		$946.5066	$946.52	$946.50	$946.60