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 $24.44   8.378%   $26.4876   $26.49   $26.50   $26.50  
  Purchase #2 $222.65   11.157%   $247.4911   $247.49   $247.50   $247.50  
  Purchase #3 $126.39   4.429%   $131.9878   $131.99   $132.00   $132.00  
  Purchase #4 $53.35   6.384%   $56.7559   $56.76   $56.75   $56.80  
  Purchase #5 $209.31   3.639%   $216.9268   $216.93   $216.95   $216.90  
  Purchase #6 $232.75   4.609%   $243.4774   $243.48   $243.50   $243.50  
  Purchase #7 $213.71   7.599%   $229.9498   $229.95   $229.95   $229.90  
  7 purchase totals = $1,082.60       $1,153.0764   $1,153.09   $1,153.15   $1,153.10