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	$63.94	5.316%	$67.3391	$67.34	$67.35	$67.30
Purchase #2	$97.98	3.510%	$101.4191	$101.42	$101.40	$101.40
Purchase #3	$161.31	4.291%	$168.2318	$168.23	$168.25	$168.20
Purchase #4	$178.95	11.216%	$199.021	$199.02	$199.00	$199.00
Purchase #5	$117.97	13.657%	$134.0812	$134.08	$134.10	$134.10
Purchase #6	$192.41	12.714%	$216.873	$216.87	$216.85	$216.90
Purchase #7	$53.32	11.633%	$59.5227	$59.52	$59.50	$59.50
7 purchase totals =	$865.88		$946.4879	$946.48	$946.45	$946.40