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 $176.26   8.259%   $190.8173   $190.82   $190.80   $190.80  
  Purchase #2 $128.66   4.116%   $133.9556   $133.96   $133.95   $134.00  
  Purchase #3 $191.25   3.349%   $197.655   $197.66   $197.65   $197.70  
  Purchase #4 $64.63   8.151%   $69.898   $69.90   $69.90   $69.90  
  Purchase #5 $183.89   6.398%   $195.6553   $195.66   $195.65   $195.70  
  Purchase #6 $93.73   4.832%   $98.259   $98.26   $98.25   $98.30  
  Purchase #7 $183.84   13.112%   $207.9451   $207.95   $207.95   $207.90  
  7 purchase totals = $1,022.26       $1,094.1853   $1,094.21   $1,094.15   $1,094.30