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 $88.56   6.760%   $94.5467   $94.55   $94.55   $94.50  
  Purchase #2 $231.97   12.614%   $261.2307   $261.23   $261.25   $261.20  
  Purchase #3 $173.38   7.368%   $186.1546   $186.15   $186.15   $186.20  
  Purchase #4 $31.90   6.508%   $33.9761   $33.98   $34.00   $34.00  
  Purchase #5 $230.26   5.793%   $243.599   $243.60   $243.60   $243.60  
  Purchase #6 $44.60   3.611%   $46.2105   $46.21   $46.20   $46.20  
  Purchase #7 $187.75   4.604%   $196.394   $196.39   $196.40   $196.40  
  7 purchase totals = $988.42       $1,062.1116   $1,062.11   $1,062.15   $1,062.10