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 $169.87   4.806%   $178.034   $178.03   $178.05   $178.00  
  Purchase #2 $106.38   5.583%   $112.3192   $112.32   $112.30   $112.30  
  Purchase #3 $89.46   6.696%   $95.4502   $95.45   $95.45   $95.50  
  Purchase #4 $161.55   5.257%   $170.0427   $170.04   $170.05   $170.00  
  Purchase #5 $118.57   11.146%   $131.7858   $131.79   $131.80   $131.80  
  Purchase #6 $198.44   4.338%   $207.0483   $207.05   $207.05   $207.00  
  Purchase #7 $201.47   4.859%   $211.2594   $211.26   $211.25   $211.30  
  7 purchase totals = $1,045.74       $1,105.9396   $1,105.94   $1,105.95   $1,105.90