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	$36.40	13.265%	$41.2285	$41.23	$41.25	$41.20
Purchase #2	$44.25	6.598%	$47.1696	$47.17	$47.15	$47.20
Purchase #3	$72.95	9.772%	$80.0787	$80.08	$80.10	$80.10
Purchase #4	$102.92	8.761%	$111.9368	$111.94	$111.95	$111.90
Purchase #5	$23.94	12.621%	$26.9615	$26.96	$26.95	$27.00
Purchase #6	$226.32	6.321%	$240.6257	$240.63	$240.65	$240.60
Purchase #7	$217.57	9.797%	$238.8853	$238.89	$238.90	$238.90
7 purchase totals =	$724.35		$786.8861	$786.90	$786.95	$786.90