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 $87.71   9.159%   $95.7434   $95.74   $95.75   $95.70  
  Purchase #2 $221.34   9.144%   $241.5793   $241.58   $241.60   $241.60  
  Purchase #3 $223.48   9.790%   $245.3587   $245.36   $245.35   $245.40  
  Purchase #4 $164.69   8.276%   $178.3197   $178.32   $178.30   $178.30  
  Purchase #5 $247.30   7.518%   $265.892   $265.89   $265.90   $265.90  
  Purchase #6 $184.73   6.712%   $197.1291   $197.13   $197.15   $197.10  
  Purchase #7 $90.47   13.165%   $102.3804   $102.38   $102.40   $102.40  
  7 purchase totals = $1,219.72       $1,326.4026   $1,326.40   $1,326.45   $1,326.40