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 $34.95   5.492%   $36.8695   $36.87   $36.85   $36.90  
  Purchase #2 $167.72   8.682%   $182.2815   $182.28   $182.30   $182.30  
  Purchase #3 $201.40   13.282%   $228.1499   $228.15   $228.15   $228.10  
  Purchase #4 $66.63   9.472%   $72.9412   $72.94   $72.95   $72.90  
  Purchase #5 $152.90   11.202%   $170.0279   $170.03   $170.05   $170.00  
  Purchase #6 $240.29   9.184%   $262.3582   $262.36   $262.35   $262.40  
  Purchase #7 $137.88   4.356%   $143.8861   $143.89   $143.90   $143.90  
  7 purchase totals = $1,001.77       $1,096.5143   $1,096.52   $1,096.55   $1,096.50