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 $156.54   4.259%   $163.207   $163.21   $163.20   $163.20  
  Purchase #2 $242.82   9.459%   $265.7883   $265.79   $265.80   $265.80  
  Purchase #3 $60.34   11.282%   $67.1476   $67.15   $67.15   $67.10  
  Purchase #4 $131.94   3.384%   $136.4048   $136.40   $136.40   $136.40  
  Purchase #5 $62.52   6.449%   $66.5519   $66.55   $66.55   $66.60  
  Purchase #6 $35.90   5.766%   $37.97   $37.97   $37.95   $38.00  
  Purchase #7 $226.89   13.807%   $258.2167   $258.22   $258.20   $258.20  
  7 purchase totals = $916.95       $995.2863   $995.29   $995.25   $995.30