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 $69.28   3.224%   $71.5136   $71.51   $71.50   $71.50  
  Purchase #2 $187.69   5.439%   $197.8985   $197.90   $197.90   $197.90  
  Purchase #3 $156.87   8.689%   $170.5004   $170.50   $170.50   $170.50  
  Purchase #4 $230.68   11.828%   $257.9648   $257.96   $257.95   $258.00  
  Purchase #5 $179.52   12.452%   $201.8738   $201.87   $201.85   $201.90  
  Purchase #6 $146.78   12.670%   $165.377   $165.38   $165.40   $165.40  
  Purchase #7 $151.64   6.305%   $161.2009   $161.20   $161.20   $161.20  
  7 purchase totals = $1,122.46       $1,226.3290   $1,226.32   $1,226.30   $1,226.40