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 $217.56   8.411%   $235.859   $235.86   $235.85   $235.90  
  Purchase #2 $67.95   10.491%   $75.0786   $75.08   $75.10   $75.10  
  Purchase #3 $83.33   6.268%   $88.5531   $88.55   $88.55   $88.60  
  Purchase #4 $247.62   8.619%   $268.9624   $268.96   $268.95   $269.00  
  Purchase #5 $166.55   8.602%   $180.8766   $180.88   $180.90   $180.90  
  Purchase #6 $160.76   13.421%   $182.3356   $182.34   $182.35   $182.30  
  Purchase #7 $168.52   13.452%   $191.1893   $191.19   $191.20   $191.20  
  7 purchase totals = $1,112.29       $1,222.8546   $1,222.86   $1,222.90   $1,223.00