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 $195.96   10.671%   $216.8709   $216.87   $216.85   $216.90  
  Purchase #2 $180.99   10.418%   $199.8455   $199.85   $199.85   $199.80  
  Purchase #3 $94.29   4.309%   $98.353   $98.35   $98.35   $98.40  
  Purchase #4 $173.39   13.366%   $196.5653   $196.57   $196.55   $196.60  
  Purchase #5 $67.28   12.866%   $75.9362   $75.94   $75.95   $75.90  
  Purchase #6 $94.47   12.524%   $106.3014   $106.30   $106.30   $106.30  
  Purchase #7 $249.48   11.295%   $277.6588   $277.66   $277.65   $277.70  
  7 purchase totals = $1,055.86       $1,171.5311   $1,171.54   $1,171.50   $1,171.60