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 $92.76   4.516%   $96.949   $96.95   $96.95   $96.90  
  Purchase #2 $170.33   6.635%   $181.6314   $181.63   $181.65   $181.60  
  Purchase #3 $79.69   7.507%   $85.6723   $85.67   $85.65   $85.70  
  Purchase #4 $57.58   3.828%   $59.7842   $59.78   $59.80   $59.80  
  Purchase #5 $245.98   5.783%   $260.205   $260.21   $260.20   $260.20  
  Purchase #6 $83.45   10.557%   $92.2598   $92.26   $92.25   $92.30  
  Purchase #7 $15.41   5.750%   $16.2961   $16.30   $16.30   $16.30  
  7 purchase totals = $745.20       $792.7978   $792.80   $792.80   $792.80