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	$92.36	10.688%	$102.2314	$102.23	$102.25	$102.20
Purchase #2	$177.46	10.857%	$196.7268	$196.73	$196.75	$196.70
Purchase #3	$104.88	6.692%	$111.8986	$111.90	$111.90	$111.90
Purchase #4	$136.60	6.331%	$145.2481	$145.25	$145.25	$145.20
Purchase #5	$196.34	13.574%	$222.9912	$222.99	$223.00	$223.00
Purchase #6	$14.53	13.107%	$16.4344	$16.43	$16.45	$16.40
Purchase #7	$116.36	6.797%	$124.269	$124.27	$124.25	$124.30
7 purchase totals =	$838.53		$919.7995	$919.80	$919.85	$919.70