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 $103.82   10.616%   $114.8415   $114.84   $114.85   $114.80  
  Purchase #2 $174.39   12.238%   $195.7318   $195.73   $195.75   $195.70  
  Purchase #3 $204.25   12.253%   $229.2768   $229.28   $229.30   $229.30  
  Purchase #4 $207.79   8.453%   $225.3545   $225.35   $225.35   $225.40  
  Purchase #5 $217.59   12.648%   $245.1108   $245.11   $245.10   $245.10  
  Purchase #6 $224.31   13.309%   $254.1634   $254.16   $254.15   $254.20  
  Purchase #7 $81.39   7.841%   $87.7718   $87.77   $87.75   $87.80  
  7 purchase totals = $1,213.54       $1,352.2506   $1,352.24   $1,352.25   $1,352.30