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 $186.48   3.856%   $193.6707   $193.67   $193.65   $193.70  
  Purchase #2 $64.42   11.216%   $71.6453   $71.65   $71.65   $71.60  
  Purchase #3 $129.62   11.157%   $144.0817   $144.08   $144.10   $144.10  
  Purchase #4 $23.86   9.224%   $26.0608   $26.06   $26.05   $26.10  
  Purchase #5 $232.75   7.829%   $250.972   $250.97   $250.95   $251.00  
  Purchase #6 $165.58   5.666%   $174.9618   $174.96   $174.95   $175.00  
  Purchase #7 $188.81   6.375%   $200.8466   $200.85   $200.85   $200.80  
  7 purchase totals = $991.52       $1,062.2389   $1,062.24   $1,062.20   $1,062.30