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 $86.90   6.499%   $92.5476   $92.55   $92.55   $92.50  
  Purchase #2 $34.71   4.550%   $36.2893   $36.29   $36.30   $36.30  
  Purchase #3 $243.42   4.571%   $254.5467   $254.55   $254.55   $254.50  
  Purchase #4 $243.77   10.228%   $268.7028   $268.70   $268.70   $268.70  
  Purchase #5 $208.90   5.270%   $219.909   $219.91   $219.90   $219.90  
  Purchase #6 $249.32   6.638%   $265.8699   $265.87   $265.85   $265.90  
  Purchase #7 $5.80   8.738%   $6.3068   $6.31   $6.30   $6.30  
  7 purchase totals = $1,072.82       $1,144.1721   $1,144.18   $1,144.15   $1,144.10