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 $88.67   7.169%   $95.0268   $95.03   $95.05   $95.00  
  Purchase #2 $227.75   7.832%   $245.5874   $245.59   $245.60   $245.60  
  Purchase #3 $195.78   4.740%   $205.06   $205.06   $205.05   $205.10  
  Purchase #4 $85.83   13.662%   $97.5561   $97.56   $97.55   $97.60  
  Purchase #5 $84.83   8.540%   $92.0745   $92.07   $92.05   $92.10  
  Purchase #6 $194.71   4.531%   $203.5323   $203.53   $203.55   $203.50  
  Purchase #7 $157.76   7.873%   $170.1804   $170.18   $170.20   $170.20  
  7 purchase totals = $1,035.33       $1,109.0175   $1,109.02   $1,109.05   $1,109.10