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 $41.63   11.834%   $46.5565   $46.56   $46.55   $46.60  
  Purchase #2 $192.30   6.702%   $205.1879   $205.19   $205.20   $205.20  
  Purchase #3 $34.93   6.167%   $37.0841   $37.08   $37.10   $37.10  
  Purchase #4 $190.31   8.359%   $206.218   $206.22   $206.20   $206.20  
  Purchase #5 $197.37   6.535%   $210.2681   $210.27   $210.25   $210.30  
  Purchase #6 $198.90   12.154%   $223.0743   $223.07   $223.05   $223.10  
  Purchase #7 $50.81   8.641%   $55.2005   $55.20   $55.20   $55.20  
  7 purchase totals = $906.25       $983.5894   $983.59   $983.55   $983.70