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 $41.77   12.654%   $47.0556   $47.06   $47.05   $47.10  
  Purchase #2 $238.65   5.363%   $251.4488   $251.45   $251.45   $251.40  
  Purchase #3 $63.80   5.678%   $67.4226   $67.42   $67.40   $67.40  
  Purchase #4 $153.37   12.231%   $172.1287   $172.13   $172.15   $172.10  
  Purchase #5 $54.37   4.164%   $56.634   $56.63   $56.65   $56.60  
  Purchase #6 $130.36   5.447%   $137.4607   $137.46   $137.45   $137.50  
  Purchase #7 $189.66   7.867%   $204.5806   $204.58   $204.60   $204.60  
  7 purchase totals = $871.98       $936.7310   $936.73   $936.75   $936.70