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 $238.36   4.441%   $248.9456   $248.95   $248.95   $248.90  
  Purchase #2 $226.98   12.316%   $254.9349   $254.93   $254.95   $254.90  
  Purchase #3 $164.44   6.420%   $174.997   $175.00   $175.00   $175.00  
  Purchase #4 $42.37   8.645%   $46.0329   $46.03   $46.05   $46.00  
  Purchase #5 $174.70   7.529%   $187.8532   $187.85   $187.85   $187.90  
  Purchase #6 $37.40   5.847%   $39.5868   $39.59   $39.60   $39.60  
  Purchase #7 $181.50   12.699%   $204.5487   $204.55   $204.55   $204.50  
  7 purchase totals = $1,065.75       $1,156.8991   $1,156.90   $1,156.95   $1,156.80