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 $41.88   10.523%   $46.287   $46.29   $46.30   $46.30  
  Purchase #2 $224.90   3.448%   $232.6546   $232.65   $232.65   $232.70  
  Purchase #3 $53.25   11.202%   $59.2151   $59.22   $59.20   $59.20  
  Purchase #4 $168.33   10.312%   $185.6882   $185.69   $185.70   $185.70  
  Purchase #5 $31.86   5.371%   $33.5712   $33.57   $33.55   $33.60  
  Purchase #6 $233.68   3.850%   $242.6767   $242.68   $242.70   $242.70  
  Purchase #7 $225.54   8.692%   $245.1439   $245.14   $245.15   $245.10  
  7 purchase totals = $979.44       $1,045.2367   $1,045.24   $1,045.25   $1,045.30