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 $114.73   3.432%   $118.6675   $118.67   $118.65   $118.70  
  Purchase #2 $238.94   9.594%   $261.8639   $261.86   $261.85   $261.90  
  Purchase #3 $123.67   7.446%   $132.8785   $132.88   $132.90   $132.90  
  Purchase #4 $245.54   3.278%   $253.5888   $253.59   $253.60   $253.60  
  Purchase #5 $177.64   6.511%   $189.2061   $189.21   $189.20   $189.20  
  Purchase #6 $196.55   5.731%   $207.8143   $207.81   $207.80   $207.80  
  Purchase #7 $187.73   6.817%   $200.5276   $200.53   $200.55   $200.50  
  7 purchase totals = $1,284.80       $1,364.5467   $1,364.55   $1,364.55   $1,364.60