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 $118.93   5.174%   $125.0834   $125.08   $125.10   $125.10  
  Purchase #2 $180.85   12.622%   $203.6769   $203.68   $203.70   $203.70  
  Purchase #3 $54.73   11.766%   $61.1695   $61.17   $61.15   $61.20  
  Purchase #4 $168.86   11.579%   $188.4123   $188.41   $188.40   $188.40  
  Purchase #5 $140.78   4.575%   $147.2207   $147.22   $147.20   $147.20  
  Purchase #6 $79.56   5.760%   $84.1427   $84.14   $84.15   $84.10  
  Purchase #7 $58.49   12.773%   $65.9609   $65.96   $65.95   $66.00  
  7 purchase totals = $802.20       $875.6664   $875.66   $875.65   $875.70