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 $97.81   4.584%   $102.2936   $102.29   $102.30   $102.30  
  Purchase #2 $225.42   4.236%   $234.9688   $234.97   $234.95   $235.00  
  Purchase #3 $182.83   5.631%   $193.1252   $193.13   $193.15   $193.10  
  Purchase #4 $199.62   7.496%   $214.5835   $214.58   $214.60   $214.60  
  Purchase #5 $62.54   4.136%   $65.1267   $65.13   $65.15   $65.10  
  Purchase #6 $211.28   5.113%   $222.0827   $222.08   $222.10   $222.10  
  Purchase #7 $195.39   4.781%   $204.7316   $204.73   $204.75   $204.70  
  7 purchase totals = $1,174.89       $1,236.9121   $1,236.91   $1,237.00   $1,236.90