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 $47.95   12.871%   $54.1216   $54.12   $54.10   $54.10  
  Purchase #2 $128.88   6.452%   $137.1953   $137.20   $137.20   $137.20  
  Purchase #3 $117.54   12.137%   $131.8058   $131.81   $131.80   $131.80  
  Purchase #4 $162.71   4.169%   $169.4934   $169.49   $169.50   $169.50  
  Purchase #5 $140.55   8.861%   $153.0041   $153.00   $153.00   $153.00  
  Purchase #6 $190.47   5.548%   $201.0373   $201.04   $201.05   $201.00  
  Purchase #7 $160.68   12.383%   $180.577   $180.58   $180.60   $180.60  
  7 purchase totals = $948.78       $1,027.2345   $1,027.24   $1,027.25   $1,027.20