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 $146.39   5.594%   $154.5791   $154.58   $154.60   $154.60  
  Purchase #2 $106.55   10.453%   $117.6877   $117.69   $117.70   $117.70  
  Purchase #3 $222.55   5.682%   $235.1953   $235.20   $235.20   $235.20  
  Purchase #4 $193.26   5.694%   $204.2642   $204.26   $204.25   $204.30  
  Purchase #5 $79.90   7.417%   $85.8262   $85.83   $85.85   $85.80  
  Purchase #6 $158.63   5.191%   $166.8645   $166.86   $166.85   $166.90  
  Purchase #7 $216.65   6.473%   $230.6738   $230.67   $230.65   $230.70  
  7 purchase totals = $1,123.93       $1,195.0908   $1,195.09   $1,195.10   $1,195.20