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 $86.55   7.517%   $93.056   $93.06   $93.05   $93.10  
  Purchase #2 $122.49   5.558%   $129.298   $129.30   $129.30   $129.30  
  Purchase #3 $59.30   9.229%   $64.7728   $64.77   $64.75   $64.80  
  Purchase #4 $150.66   5.364%   $158.7414   $158.74   $158.75   $158.70  
  Purchase #5 $68.39   8.653%   $74.3078   $74.31   $74.30   $74.30  
  Purchase #6 $213.42   10.677%   $236.2069   $236.21   $236.20   $236.20  
  Purchase #7 $192.48   10.351%   $212.4036   $212.40   $212.40   $212.40  
  7 purchase totals = $893.29       $968.7865   $968.79   $968.75   $968.80