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	$102.53	13.500%	$116.3716	$116.37	$116.35	$116.40
Purchase #2	$110.66	5.706%	$116.9743	$116.97	$116.95	$117.00
Purchase #3	$74.54	7.693%	$80.2744	$80.27	$80.25	$80.30
Purchase #4	$232.80	3.467%	$240.8712	$240.87	$240.85	$240.90
Purchase #5	$89.45	8.298%	$96.8726	$96.87	$96.85	$96.90
Purchase #6	$186.61	7.678%	$200.9379	$200.94	$200.95	$200.90
Purchase #7	$152.28	8.309%	$164.9329	$164.93	$164.95	$164.90
7 purchase totals =	$948.87		$1,017.2349	$1,017.22	$1,017.15	$1,017.30