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 $96.58   7.625%   $103.9442   $103.94   $103.95   $103.90  
  Purchase #2 $222.26   6.675%   $237.0959   $237.10   $237.10   $237.10  
  Purchase #3 $235.58   12.229%   $264.3891   $264.39   $264.40   $264.40  
  Purchase #4 $114.74   4.246%   $119.6119   $119.61   $119.60   $119.60  
  Purchase #5 $93.52   9.788%   $102.6737   $102.67   $102.65   $102.70  
  Purchase #6 $175.27   4.534%   $183.2167   $183.22   $183.20   $183.20  
  Purchase #7 $25.46   5.504%   $26.8613   $26.86   $26.85   $26.90  
  7 purchase totals = $963.41       $1,037.7928   $1,037.79   $1,037.75   $1,037.80