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 $64.54   5.288%   $67.9529   $67.95   $67.95   $68.00  
  Purchase #2 $164.84   3.710%   $170.9556   $170.96   $170.95   $171.00  
  Purchase #3 $210.48   8.598%   $228.5771   $228.58   $228.60   $228.60  
  Purchase #4 $222.29   12.434%   $249.9295   $249.93   $249.95   $249.90  
  Purchase #5 $235.92   7.832%   $254.3973   $254.40   $254.40   $254.40  
  Purchase #6 $195.60   8.359%   $211.9502   $211.95   $211.95   $212.00  
  Purchase #7 $232.31   6.382%   $247.136   $247.14   $247.15   $247.10  
  7 purchase totals = $1,325.98       $1,430.8986   $1,430.91   $1,430.95   $1,431.00