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 $118.66   6.153%   $125.9611   $125.96   $125.95   $126.00  
  Purchase #2 $149.74   7.750%   $161.3449   $161.34   $161.35   $161.30  
  Purchase #3 $72.44   13.275%   $82.0564   $82.06   $82.05   $82.10  
  Purchase #4 $111.25   8.143%   $120.3091   $120.31   $120.30   $120.30  
  Purchase #5 $88.54   8.342%   $95.926   $95.93   $95.95   $95.90  
  Purchase #6 $17.62   11.628%   $19.6689   $19.67   $19.65   $19.70  
  Purchase #7 $136.93   5.400%   $144.3242   $144.32   $144.30   $144.30  
  7 purchase totals = $695.18       $749.5906   $749.59   $749.55   $749.60