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 $65.86   5.328%   $69.369   $69.37   $69.35   $69.40  
  Purchase #2 $237.88   12.778%   $268.2763   $268.28   $268.30   $268.30  
  Purchase #3 $118.91   8.450%   $128.9579   $128.96   $128.95   $129.00  
  Purchase #4 $199.80   4.826%   $209.4423   $209.44   $209.45   $209.40  
  Purchase #5 $117.95   6.151%   $125.2051   $125.21   $125.20   $125.20  
  Purchase #6 $244.90   11.641%   $273.4088   $273.41   $273.40   $273.40  
  Purchase #7 $41.91   6.662%   $44.702   $44.70   $44.70   $44.70  
  7 purchase totals = $1,027.21       $1,119.3614   $1,119.37   $1,119.35   $1,119.40