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 $59.46   11.867%   $66.5161   $66.52   $66.50   $66.50  
  Purchase #2 $140.92   9.708%   $154.6005   $154.60   $154.60   $154.60  
  Purchase #3 $70.47   8.393%   $76.3845   $76.38   $76.40   $76.40  
  Purchase #4 $155.94   7.611%   $167.8086   $167.81   $167.80   $167.80  
  Purchase #5 $245.40   11.309%   $273.1523   $273.15   $273.15   $273.20  
  Purchase #6 $182.44   11.743%   $203.8639   $203.86   $203.85   $203.90  
  Purchase #7 $53.79   8.180%   $58.19   $58.19   $58.20   $58.20  
  7 purchase totals = $908.42       $1,000.5159   $1,000.51   $1,000.50   $1,000.60