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 $84.68   9.672%   $92.8702   $92.87   $92.85   $92.90  
  Purchase #2 $205.72   4.709%   $215.4074   $215.41   $215.40   $215.40  
  Purchase #3 $146.35   11.113%   $162.6139   $162.61   $162.60   $162.60  
  Purchase #4 $121.64   11.417%   $135.5276   $135.53   $135.55   $135.50  
  Purchase #5 $193.51   10.144%   $213.1397   $213.14   $213.15   $213.10  
  Purchase #6 $235.99   9.373%   $258.1093   $258.11   $258.10   $258.10  
  Purchase #7 $119.48   6.224%   $126.9164   $126.92   $126.90   $126.90  
  7 purchase totals = $1,107.37       $1,204.5845   $1,204.59   $1,204.55   $1,204.50