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 $17.84   7.266%   $19.1363   $19.14   $19.15   $19.10  
  Purchase #2 $208.58   10.402%   $230.2765   $230.28   $230.30   $230.30  
  Purchase #3 $152.45   9.542%   $166.9968   $167.00   $167.00   $167.00  
  Purchase #4 $182.35   9.306%   $199.3195   $199.32   $199.30   $199.30  
  Purchase #5 $154.86   13.474%   $175.7258   $175.73   $175.75   $175.70  
  Purchase #6 $162.67   5.223%   $171.1663   $171.17   $171.15   $171.20  
  Purchase #7 $57.43   10.289%   $63.339   $63.34   $63.35   $63.30  
  7 purchase totals = $936.18       $1,025.9602   $1,025.98   $1,026.00   $1,025.90