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 $183.49   7.390%   $197.0499   $197.05   $197.05   $197.00  
  Purchase #2 $143.27   9.115%   $156.3291   $156.33   $156.35   $156.30  
  Purchase #3 $15.37   12.233%   $17.2502   $17.25   $17.25   $17.30  
  Purchase #4 $69.88   6.554%   $74.4599   $74.46   $74.45   $74.50  
  Purchase #5 $163.90   9.383%   $179.2787   $179.28   $179.30   $179.30  
  Purchase #6 $201.26   4.487%   $210.2905   $210.29   $210.30   $210.30  
  Purchase #7 $183.75   10.122%   $202.3492   $202.35   $202.35   $202.30  
  7 purchase totals = $960.92       $1,037.0075   $1,037.01   $1,037.05   $1,037.00