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 $119.62   4.709%   $125.2529   $125.25   $125.25   $125.30  
  Purchase #2 $22.84   3.392%   $23.6147   $23.61   $23.60   $23.60  
  Purchase #3 $148.34   12.494%   $166.8736   $166.87   $166.85   $166.90  
  Purchase #4 $175.42   3.530%   $181.6123   $181.61   $181.60   $181.60  
  Purchase #5 $229.90   9.273%   $251.2186   $251.22   $251.20   $251.20  
  Purchase #6 $196.29   11.798%   $219.4483   $219.45   $219.45   $219.40  
  Purchase #7 $246.39   6.427%   $262.2255   $262.23   $262.25   $262.20  
  7 purchase totals = $1,138.80       $1,230.2459   $1,230.24   $1,230.20   $1,230.20