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	$162.72	10.348%	$179.5583	$179.56	$179.55	$179.60
Purchase #2	$67.72	12.823%	$76.4037	$76.40	$76.40	$76.40
Purchase #3	$71.44	10.493%	$78.9362	$78.94	$78.95	$78.90
Purchase #4	$212.35	3.610%	$220.0158	$220.02	$220.00	$220.00
Purchase #5	$68.56	7.701%	$73.8398	$73.84	$73.85	$73.80
Purchase #6	$63.49	4.457%	$66.3197	$66.32	$66.30	$66.30
Purchase #7	$65.50	4.456%	$68.4187	$68.42	$68.40	$68.40
7 purchase totals =	$711.78		$763.4922	$763.50	$763.45	$763.40