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 $162.94   12.156%   $182.747   $182.75   $182.75   $182.70  
  Purchase #2 $197.87   9.677%   $217.0179   $217.02   $217.00   $217.00  
  Purchase #3 $218.59   7.313%   $234.5755   $234.58   $234.60   $234.60  
  Purchase #4 $41.94   9.483%   $45.9172   $45.92   $45.90   $45.90  
  Purchase #5 $67.69   13.774%   $77.0136   $77.01   $77.00   $77.00  
  Purchase #6 $73.51   13.535%   $83.4596   $83.46   $83.45   $83.50  
  Purchase #7 $103.56   6.430%   $110.2189   $110.22   $110.20   $110.20  
  7 purchase totals = $866.10       $950.9497   $950.96   $950.90   $950.90