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 $58.72   5.533%   $61.969   $61.97   $61.95   $62.00  
  Purchase #2 $52.43   13.761%   $59.6449   $59.64   $59.65   $59.60  
  Purchase #3 $148.82   7.779%   $160.3967   $160.40   $160.40   $160.40  
  Purchase #4 $219.68   6.447%   $233.8428   $233.84   $233.85   $233.80  
  Purchase #5 $186.55   9.863%   $204.9494   $204.95   $204.95   $204.90  
  Purchase #6 $74.58   5.208%   $78.4641   $78.46   $78.45   $78.50  
  Purchase #7 $144.90   11.614%   $161.7287   $161.73   $161.75   $161.70  
  7 purchase totals = $885.68       $960.9956   $960.99   $961.00   $960.90