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 $114.82   3.423%   $118.7503   $118.75   $118.75   $118.80  
  Purchase #2 $242.39   8.425%   $262.8114   $262.81   $262.80   $262.80  
  Purchase #3 $80.28   3.567%   $83.1436   $83.14   $83.15   $83.10  
  Purchase #4 $150.52   11.846%   $168.3506   $168.35   $168.35   $168.40  
  Purchase #5 $169.34   5.218%   $178.1762   $178.18   $178.20   $178.20  
  Purchase #6 $16.28   9.569%   $17.8378   $17.84   $17.85   $17.80  
  Purchase #7 $225.97   3.179%   $233.1536   $233.15   $233.15   $233.20  
  7 purchase totals = $999.60       $1,062.2235   $1,062.22   $1,062.25   $1,062.30