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 $62.37   13.399%   $70.727   $70.73   $70.75   $70.70  
  Purchase #2 $208.97   4.725%   $218.8438   $218.84   $218.85   $218.80  
  Purchase #3 $193.95   3.212%   $200.1797   $200.18   $200.20   $200.20  
  Purchase #4 $220.83   11.375%   $245.9494   $245.95   $245.95   $245.90  
  Purchase #5 $136.48   10.159%   $150.345   $150.35   $150.35   $150.30  
  Purchase #6 $23.27   5.694%   $24.595   $24.60   $24.60   $24.60  
  Purchase #7 $188.90   4.272%   $196.9698   $196.97   $196.95   $197.00  
  7 purchase totals = $1,034.77       $1,107.6097   $1,107.62   $1,107.65   $1,107.50