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 $91.80   4.232%   $95.685   $95.69   $95.70   $95.70  
  Purchase #2 $241.89   12.425%   $271.9448   $271.94   $271.95   $271.90  
  Purchase #3 $193.70   5.775%   $204.8862   $204.89   $204.90   $204.90  
  Purchase #4 $134.69   8.327%   $145.9056   $145.91   $145.90   $145.90  
  Purchase #5 $17.26   12.488%   $19.4154   $19.42   $19.40   $19.40  
  Purchase #6 $58.42   6.240%   $62.0654   $62.07   $62.05   $62.10  
  Purchase #7 $247.94   4.224%   $258.413   $258.41   $258.40   $258.40  
  7 purchase totals = $985.70       $1,058.3154   $1,058.33   $1,058.30   $1,058.30