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 $91.75   4.254%   $95.653   $95.65   $95.65   $95.70  
  Purchase #2 $50.49   5.298%   $53.165   $53.17   $53.15   $53.20  
  Purchase #3 $62.48   12.493%   $70.2856   $70.29   $70.30   $70.30  
  Purchase #4 $68.82   13.331%   $77.9944   $77.99   $78.00   $78.00  
  Purchase #5 $206.46   12.645%   $232.5669   $232.57   $232.55   $232.60  
  Purchase #6 $162.81   9.606%   $178.4495   $178.45   $178.45   $178.40  
  Purchase #7 $87.73   10.753%   $97.1636   $97.16   $97.15   $97.20  
  7 purchase totals = $730.54       $805.2780   $805.28   $805.25   $805.40