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 $193.97   4.276%   $202.2642   $202.26   $202.25   $202.30  
  Purchase #2 $109.33   13.607%   $124.2065   $124.21   $124.20   $124.20  
  Purchase #3 $140.48   11.407%   $156.5046   $156.50   $156.50   $156.50  
  Purchase #4 $181.63   9.245%   $198.4217   $198.42   $198.40   $198.40  
  Purchase #5 $82.67   4.303%   $86.2273   $86.23   $86.25   $86.20  
  Purchase #6 $148.88   4.567%   $155.6793   $155.68   $155.70   $155.70  
  Purchase #7 $96.25   4.485%   $100.5668   $100.57   $100.55   $100.60  
  7 purchase totals = $953.21       $1,023.8704   $1,023.87   $1,023.85   $1,023.90