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 $40.59   13.284%   $45.982   $45.98   $46.00   $46.00  
  Purchase #2 $121.71   3.829%   $126.3703   $126.37   $126.35   $126.40  
  Purchase #3 $193.77   11.209%   $215.4897   $215.49   $215.50   $215.50  
  Purchase #4 $49.31   8.379%   $53.4417   $53.44   $53.45   $53.40  
  Purchase #5 $209.38   9.337%   $228.9298   $228.93   $228.95   $228.90  
  Purchase #6 $118.54   12.193%   $132.9936   $132.99   $133.00   $133.00  
  Purchase #7 $223.43   12.828%   $252.0916   $252.09   $252.10   $252.10  
  7 purchase totals = $956.73       $1,055.2987   $1,055.29   $1,055.35   $1,055.30