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 $113.91   11.426%   $126.9254   $126.93   $126.95   $126.90  
  Purchase #2 $207.58   11.584%   $231.6261   $231.63   $231.65   $231.60  
  Purchase #3 $166.41   7.414%   $178.7476   $178.75   $178.75   $178.70  
  Purchase #4 $49.44   5.837%   $52.3258   $52.33   $52.35   $52.30  
  Purchase #5 $214.91   5.489%   $226.7064   $226.71   $226.70   $226.70  
  Purchase #6 $131.54   7.639%   $141.5883   $141.59   $141.60   $141.60  
  Purchase #7 $188.26   12.132%   $211.0997   $211.10   $211.10   $211.10  
  7 purchase totals = $1,072.05       $1,169.0193   $1,169.04   $1,169.10   $1,168.90