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 $182.56   8.136%   $197.4131   $197.41   $197.40   $197.40  
  Purchase #2 $174.67   8.517%   $189.5466   $189.55   $189.55   $189.50  
  Purchase #3 $216.29   6.217%   $229.7367   $229.74   $229.75   $229.70  
  Purchase #4 $186.62   3.483%   $193.12   $193.12   $193.10   $193.10  
  Purchase #5 $230.90   5.547%   $243.708   $243.71   $243.70   $243.70  
  Purchase #6 $5.86   5.829%   $6.2016   $6.20   $6.20   $6.20  
  Purchase #7 $95.39   7.805%   $102.8352   $102.84   $102.85   $102.80  
  7 purchase totals = $1,092.29       $1,162.5612   $1,162.57   $1,162.55   $1,162.40