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 $195.45   9.520%   $214.0568   $214.06   $214.05   $214.10  
  Purchase #2 $39.62   11.170%   $44.0456   $44.05   $44.05   $44.00  
  Purchase #3 $67.61   13.435%   $76.6934   $76.69   $76.70   $76.70  
  Purchase #4 $241.62   3.405%   $249.8472   $249.85   $249.85   $249.80  
  Purchase #5 $102.67   9.118%   $112.0315   $112.03   $112.05   $112.00  
  Purchase #6 $64.88   4.753%   $67.9637   $67.96   $67.95   $68.00  
  Purchase #7 $248.37   7.238%   $266.347   $266.35   $266.35   $266.30  
  7 purchase totals = $960.22       $1,030.9852   $1,030.99   $1,031.00   $1,030.90