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 $175.47   11.247%   $195.2051   $195.21   $195.20   $195.20  
  Purchase #2 $142.73   8.407%   $154.7293   $154.73   $154.75   $154.70  
  Purchase #3 $28.93   6.369%   $30.7726   $30.77   $30.75   $30.80  
  Purchase #4 $204.42   3.420%   $211.4112   $211.41   $211.40   $211.40  
  Purchase #5 $102.82   4.233%   $107.1724   $107.17   $107.15   $107.20  
  Purchase #6 $219.75   10.359%   $242.5139   $242.51   $242.50   $242.50  
  Purchase #7 $250.46   7.213%   $268.5257   $268.53   $268.55   $268.50  
  7 purchase totals = $1,124.58       $1,210.3302   $1,210.33   $1,210.30   $1,210.30