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 $61.84   6.650%   $65.9524   $65.95   $65.95   $66.00  
  Purchase #2 $117.79   3.765%   $122.2248   $122.22   $122.20   $122.20  
  Purchase #3 $176.69   9.550%   $193.5639   $193.56   $193.55   $193.60  
  Purchase #4 $193.62   5.175%   $203.6398   $203.64   $203.65   $203.60  
  Purchase #5 $136.36   5.773%   $144.2321   $144.23   $144.25   $144.20  
  Purchase #6 $167.28   6.259%   $177.7501   $177.75   $177.75   $177.80  
  Purchase #7 $162.29   7.221%   $174.009   $174.01   $174.00   $174.00  
  7 purchase totals = $1,015.87       $1,081.3721   $1,081.36   $1,081.35   $1,081.40