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 $193.27   4.404%   $201.7816   $201.78   $201.80   $201.80  
  Purchase #2 $192.58   13.104%   $217.8157   $217.82   $217.80   $217.80  
  Purchase #3 $15.55   3.183%   $16.045   $16.05   $16.05   $16.00  
  Purchase #4 $80.72   6.816%   $86.2219   $86.22   $86.20   $86.20  
  Purchase #5 $82.74   11.204%   $92.0102   $92.01   $92.00   $92.00  
  Purchase #6 $157.88   5.605%   $166.7292   $166.73   $166.75   $166.70  
  Purchase #7 $232.81   9.609%   $255.1807   $255.18   $255.20   $255.20  
  7 purchase totals = $955.55       $1,035.7843   $1,035.79   $1,035.80   $1,035.70