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 $91.38   4.269%   $95.281   $95.28   $95.30   $95.30  
  Purchase #2 $221.48   9.719%   $243.0056   $243.01   $243.00   $243.00  
  Purchase #3 $165.40   7.424%   $177.6793   $177.68   $177.70   $177.70  
  Purchase #4 $213.32   13.836%   $242.835   $242.84   $242.85   $242.80  
  Purchase #5 $245.28   5.599%   $259.0132   $259.01   $259.00   $259.00  
  Purchase #6 $130.48   6.519%   $138.986   $138.99   $139.00   $139.00  
  Purchase #7 $104.92   11.244%   $116.7172   $116.72   $116.70   $116.70  
  7 purchase totals = $1,172.26       $1,273.5173   $1,273.53   $1,273.55   $1,273.50