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 $61.54   12.174%   $69.0319   $69.03   $69.05   $69.00  
  Purchase #2 $250.85   5.275%   $264.0823   $264.08   $264.10   $264.10  
  Purchase #3 $149.59   8.409%   $162.169   $162.17   $162.15   $162.20  
  Purchase #4 $148.77   5.516%   $156.9762   $156.98   $157.00   $157.00  
  Purchase #5 $175.87   10.112%   $193.654   $193.65   $193.65   $193.70  
  Purchase #6 $184.99   13.837%   $210.5871   $210.59   $210.60   $210.60  
  Purchase #7 $128.69   9.859%   $141.3775   $141.38   $141.40   $141.40  
  7 purchase totals = $1,100.30       $1,197.8780   $1,197.88   $1,197.95   $1,198.00