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 $57.33   11.109%   $63.6988   $63.70   $63.70   $63.70  
  Purchase #2 $248.86   4.250%   $259.4366   $259.44   $259.45   $259.40  
  Purchase #3 $229.72   10.294%   $253.3674   $253.37   $253.35   $253.40  
  Purchase #4 $105.42   3.607%   $109.2225   $109.22   $109.20   $109.20  
  Purchase #5 $234.41   11.148%   $260.542   $260.54   $260.55   $260.50  
  Purchase #6 $202.72   9.829%   $222.6453   $222.65   $222.65   $222.60  
  Purchase #7 $165.54   12.835%   $186.7871   $186.79   $186.80   $186.80  
  7 purchase totals = $1,244.00       $1,355.6997   $1,355.71   $1,355.70   $1,355.60