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 $62.28   4.374%   $65.0041   $65.00   $65.00   $65.00  
  Purchase #2 $218.47   11.644%   $243.9086   $243.91   $243.90   $243.90  
  Purchase #3 $94.40   11.213%   $104.9851   $104.99   $105.00   $105.00  
  Purchase #4 $193.67   6.316%   $205.9022   $205.90   $205.90   $205.90  
  Purchase #5 $191.59   11.783%   $214.165   $214.17   $214.15   $214.20  
  Purchase #6 $136.25   9.710%   $149.4799   $149.48   $149.50   $149.50  
  Purchase #7 $121.58   11.515%   $135.5799   $135.58   $135.60   $135.60  
  7 purchase totals = $1,018.24       $1,119.0248   $1,119.03   $1,119.05   $1,119.10