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 $176.62   9.503%   $193.4042   $193.40   $193.40   $193.40  
  Purchase #2 $117.58   7.106%   $125.9352   $125.94   $125.95   $125.90  
  Purchase #3 $5.27   3.379%   $5.4481   $5.45   $5.45   $5.40  
  Purchase #4 $54.61   7.391%   $58.6462   $58.65   $58.65   $58.60  
  Purchase #5 $194.59   5.754%   $205.7867   $205.79   $205.80   $205.80  
  Purchase #6 $250.57   8.636%   $272.2092   $272.21   $272.20   $272.20  
  Purchase #7 $32.67   5.848%   $34.5805   $34.58   $34.60   $34.60  
  7 purchase totals = $831.91       $896.0101   $896.02   $896.05   $895.90