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 $211.49   6.868%   $226.0151   $226.02   $226.00   $226.00  
  Purchase #2 $94.99   11.616%   $106.024   $106.02   $106.00   $106.00  
  Purchase #3 $177.40   6.798%   $189.4597   $189.46   $189.45   $189.50  
  Purchase #4 $155.84   4.738%   $163.2237   $163.22   $163.20   $163.20  
  Purchase #5 $68.95   7.544%   $74.1516   $74.15   $74.15   $74.20  
  Purchase #6 $175.67   7.284%   $188.4658   $188.47   $188.45   $188.50  
  Purchase #7 $88.96   9.768%   $97.6496   $97.65   $97.65   $97.60  
  7 purchase totals = $973.30       $1,044.9895   $1,044.99   $1,044.90   $1,045.00