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 $56.31   10.154%   $62.0277   $62.03   $62.05   $62.00  
  Purchase #2 $36.70   13.489%   $41.6505   $41.65   $41.65   $41.70  
  Purchase #3 $142.69   11.234%   $158.7198   $158.72   $158.70   $158.70  
  Purchase #4 $231.95   8.377%   $251.3805   $251.38   $251.40   $251.40  
  Purchase #5 $128.26   6.404%   $136.4738   $136.47   $136.45   $136.50  
  Purchase #6 $233.45   10.629%   $258.2634   $258.26   $258.25   $258.30  
  Purchase #7 $231.45   12.573%   $260.5502   $260.55   $260.55   $260.60  
  7 purchase totals = $1,060.81       $1,169.0659   $1,169.06   $1,169.05   $1,169.20