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 $116.72   7.506%   $125.481   $125.48   $125.50   $125.50  
  Purchase #2 $36.33   5.126%   $38.1923   $38.19   $38.20   $38.20  
  Purchase #3 $81.29   9.113%   $88.698   $88.70   $88.70   $88.70  
  Purchase #4 $104.90   6.874%   $112.1108   $112.11   $112.10   $112.10  
  Purchase #5 $180.73   12.423%   $203.1821   $203.18   $203.20   $203.20  
  Purchase #6 $53.94   7.547%   $58.0109   $58.01   $58.00   $58.00  
  Purchase #7 $103.86   11.322%   $115.619   $115.62   $115.60   $115.60  
  7 purchase totals = $677.77       $741.2941   $741.29   $741.30   $741.30