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 $247.84   7.862%   $267.3252   $267.33   $267.35   $267.30  
  Purchase #2 $105.51   9.834%   $115.8859   $115.89   $115.90   $115.90  
  Purchase #3 $56.84   5.529%   $59.9827   $59.98   $60.00   $60.00  
  Purchase #4 $162.69   8.318%   $176.2226   $176.22   $176.20   $176.20  
  Purchase #5 $229.71   12.769%   $259.0417   $259.04   $259.05   $259.00  
  Purchase #6 $143.26   13.268%   $162.2677   $162.27   $162.25   $162.30  
  Purchase #7 $150.72   6.384%   $160.342   $160.34   $160.35   $160.30  
  7 purchase totals = $1,096.57       $1,201.0678   $1,201.07   $1,201.10   $1,201.00