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 $86.80   9.828%   $95.3307   $95.33   $95.35   $95.30  
  Purchase #2 $202.45   6.459%   $215.5262   $215.53   $215.55   $215.50  
  Purchase #3 $15.47   3.697%   $16.0419   $16.04   $16.05   $16.00  
  Purchase #4 $230.28   13.708%   $261.8468   $261.85   $261.85   $261.80  
  Purchase #5 $243.36   5.829%   $257.5455   $257.55   $257.55   $257.50  
  Purchase #6 $198.36   9.437%   $217.0792   $217.08   $217.10   $217.10  
  Purchase #7 $16.62   3.291%   $17.167   $17.17   $17.15   $17.20  
  7 purchase totals = $993.34       $1,080.5373   $1,080.55   $1,080.60   $1,080.40