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 $86.27   12.467%   $97.0253   $97.03   $97.05   $97.00  
  Purchase #2 $208.67   7.871%   $225.0944   $225.09   $225.10   $225.10  
  Purchase #3 $24.26   7.729%   $26.1351   $26.14   $26.15   $26.10  
  Purchase #4 $37.46   6.637%   $39.9462   $39.95   $39.95   $39.90  
  Purchase #5 $12.80   10.213%   $14.1073   $14.11   $14.10   $14.10  
  Purchase #6 $103.75   6.391%   $110.3807   $110.38   $110.40   $110.40  
  Purchase #7 $232.58   3.798%   $241.4134   $241.41   $241.40   $241.40  
  7 purchase totals = $705.79       $754.1024   $754.11   $754.15   $754.00