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 $236.29   10.782%   $261.7668   $261.77   $261.75   $261.80  
  Purchase #2 $62.68   9.431%   $68.5914   $68.59   $68.60   $68.60  
  Purchase #3 $169.40   5.193%   $178.1969   $178.20   $178.20   $178.20  
  Purchase #4 $172.36   11.333%   $191.8936   $191.89   $191.90   $191.90  
  Purchase #5 $190.70   4.166%   $198.6446   $198.64   $198.65   $198.60  
  Purchase #6 $46.71   4.352%   $48.7428   $48.74   $48.75   $48.70  
  Purchase #7 $80.97   8.687%   $88.0039   $88.00   $88.00   $88.00  
  7 purchase totals = $959.11       $1,035.8400   $1,035.83   $1,035.85   $1,035.80