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 $191.71   7.554%   $206.1918   $206.19   $206.20   $206.20  
  Purchase #2 $194.95   3.178%   $201.1455   $201.15   $201.15   $201.10  
  Purchase #3 $165.30   13.528%   $187.6618   $187.66   $187.65   $187.70  
  Purchase #4 $53.90   10.282%   $59.442   $59.44   $59.45   $59.40  
  Purchase #5 $187.30   9.617%   $205.3126   $205.31   $205.30   $205.30  
  Purchase #6 $68.77   3.646%   $71.2774   $71.28   $71.30   $71.30  
  Purchase #7 $164.45   5.593%   $173.6477   $173.65   $173.65   $173.60  
  7 purchase totals = $1,026.38       $1,104.6788   $1,104.68   $1,104.70   $1,104.60