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	$222.34	7.464%	$238.9355	$238.94	$238.95	$238.90
Purchase #2	$190.97	9.108%	$208.3635	$208.36	$208.35	$208.40
Purchase #3	$235.46	4.601%	$246.2935	$246.29	$246.30	$246.30
Purchase #4	$90.69	10.492%	$100.2052	$100.21	$100.20	$100.20
Purchase #5	$11.59	8.307%	$12.5528	$12.55	$12.55	$12.60
Purchase #6	$40.97	8.214%	$44.3353	$44.34	$44.35	$44.30
Purchase #7	$226.63	10.430%	$250.2675	$250.27	$250.25	$250.30
7 purchase totals =	$1,018.65		$1,100.9533	$1,100.96	$1,100.95	$1,101.00