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 $85.63   10.737%   $94.8241   $94.82   $94.80   $94.80  
  Purchase #2 $114.77   10.273%   $126.5603   $126.56   $126.55   $126.60  
  Purchase #3 $22.72   5.743%   $24.0248   $24.02   $24.00   $24.00  
  Purchase #4 $137.97   10.253%   $152.1161   $152.12   $152.10   $152.10  
  Purchase #5 $152.83   9.242%   $166.9545   $166.95   $166.95   $167.00  
  Purchase #6 $247.42   7.497%   $265.9691   $265.97   $265.95   $266.00  
  Purchase #7 $203.51   12.320%   $228.5824   $228.58   $228.60   $228.60  
  7 purchase totals = $964.85       $1,059.0313   $1,059.02   $1,058.95   $1,059.10