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 $238.65   10.182%   $262.9493   $262.95   $262.95   $262.90  
  Purchase #2 $45.38   7.103%   $48.6033   $48.60   $48.60   $48.60  
  Purchase #3 $165.62   8.525%   $179.7391   $179.74   $179.75   $179.70  
  Purchase #4 $202.92   5.349%   $213.7742   $213.77   $213.75   $213.80  
  Purchase #5 $85.83   6.380%   $91.306   $91.31   $91.30   $91.30  
  Purchase #6 $135.93   7.277%   $145.8216   $145.82   $145.80   $145.80  
  Purchase #7 $228.96   13.103%   $258.9606   $258.96   $258.95   $259.00  
  7 purchase totals = $1,103.29       $1,201.1541   $1,201.15   $1,201.10   $1,201.10