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 $204.56   7.427%   $219.7527   $219.75   $219.75   $219.80  
  Purchase #2 $216.96   11.831%   $242.6285   $242.63   $242.65   $242.60  
  Purchase #3 $24.85   5.617%   $26.2458   $26.25   $26.25   $26.20  
  Purchase #4 $195.63   5.332%   $206.061   $206.06   $206.05   $206.10  
  Purchase #5 $156.80   6.372%   $166.7913   $166.79   $166.80   $166.80  
  Purchase #6 $170.81   8.465%   $185.2691   $185.27   $185.25   $185.30  
  Purchase #7 $250.53   11.653%   $279.7243   $279.72   $279.70   $279.70  
  7 purchase totals = $1,220.14       $1,326.4727   $1,326.47   $1,326.45   $1,326.50