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 $182.74   11.733%   $204.1809   $204.18   $204.20   $204.20  
  Purchase #2 $14.31   5.376%   $15.0793   $15.08   $15.10   $15.10  
  Purchase #3 $69.46   10.165%   $76.5206   $76.52   $76.50   $76.50  
  Purchase #4 $132.70   3.157%   $136.8893   $136.89   $136.90   $136.90  
  Purchase #5 $217.67   8.460%   $236.0849   $236.08   $236.10   $236.10  
  Purchase #6 $242.47   4.277%   $252.8404   $252.84   $252.85   $252.80  
  Purchase #7 $93.67   9.231%   $102.3167   $102.32   $102.30   $102.30  
  7 purchase totals = $953.02       $1,023.9121   $1,023.91   $1,023.95   $1,023.90