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 $104.56   9.841%   $114.8497   $114.85   $114.85   $114.80  
  Purchase #2 $158.43   11.846%   $177.1976   $177.20   $177.20   $177.20  
  Purchase #3 $152.87   6.611%   $162.9762   $162.98   $163.00   $163.00  
  Purchase #4 $83.35   11.817%   $93.1995   $93.20   $93.20   $93.20  
  Purchase #5 $139.96   4.613%   $146.4164   $146.42   $146.40   $146.40  
  Purchase #6 $243.88   8.237%   $263.9684   $263.97   $263.95   $264.00  
  Purchase #7 $175.89   11.132%   $195.4701   $195.47   $195.45   $195.50  
  7 purchase totals = $1,058.94       $1,154.0779   $1,154.09   $1,154.05   $1,154.10