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 $92.58   10.122%   $101.9509   $101.95   $101.95   $102.00  
  Purchase #2 $151.28   8.613%   $164.3097   $164.31   $164.30   $164.30  
  Purchase #3 $63.51   8.110%   $68.6607   $68.66   $68.65   $68.70  
  Purchase #4 $174.57   7.350%   $187.4009   $187.40   $187.40   $187.40  
  Purchase #5 $203.59   4.639%   $213.0345   $213.03   $213.05   $213.00  
  Purchase #6 $41.79   12.266%   $46.916   $46.92   $46.90   $46.90  
  Purchase #7 $207.50   11.273%   $230.8915   $230.89   $230.90   $230.90  
  7 purchase totals = $934.82       $1,013.1642   $1,013.16   $1,013.15   $1,013.20