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 $61.96   11.646%   $69.1759   $69.18   $69.20   $69.20  
  Purchase #2 $185.42   4.300%   $193.3931   $193.39   $193.40   $193.40  
  Purchase #3 $97.66   7.294%   $104.7833   $104.78   $104.80   $104.80  
  Purchase #4 $153.72   5.284%   $161.8426   $161.84   $161.85   $161.80  
  Purchase #5 $215.69   4.415%   $225.2127   $225.21   $225.20   $225.20  
  Purchase #6 $222.73   3.678%   $230.922   $230.92   $230.90   $230.90  
  Purchase #7 $153.62   7.218%   $164.7083   $164.71   $164.70   $164.70  
  7 purchase totals = $1,090.80       $1,150.0379   $1,150.03   $1,150.05   $1,150.00