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 $62.44   7.751%   $67.2797   $67.28   $67.30   $67.30  
  Purchase #2 $248.87   13.111%   $281.4993   $281.50   $281.50   $281.50  
  Purchase #3 $176.31   7.588%   $189.6884   $189.69   $189.70   $189.70  
  Purchase #4 $215.63   12.122%   $241.7687   $241.77   $241.75   $241.80  
  Purchase #5 $110.77   6.326%   $117.7773   $117.78   $117.80   $117.80  
  Purchase #6 $68.47   12.644%   $77.1273   $77.13   $77.15   $77.10  
  Purchase #7 $58.80   3.234%   $60.7016   $60.70   $60.70   $60.70  
  7 purchase totals = $941.29       $1,035.8423   $1,035.85   $1,035.90   $1,035.90