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	$111.83	13.290%	$126.6922	$126.69	$126.70	$126.70
Purchase #2	$135.61	7.633%	$145.9611	$145.96	$145.95	$146.00
Purchase #3	$153.60	7.282%	$164.7852	$164.79	$164.80	$164.80
Purchase #4	$116.53	13.182%	$131.891	$131.89	$131.90	$131.90
Purchase #5	$177.88	10.497%	$196.5521	$196.55	$196.55	$196.60
Purchase #6	$24.36	4.350%	$25.4197	$25.42	$25.40	$25.40
Purchase #7	$51.75	7.659%	$55.7135	$55.71	$55.70	$55.70
7 purchase totals =	$771.56		$847.0148	$847.01	$847.00	$847.10