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 $118.70   5.751%   $125.5264   $125.53   $125.55   $125.50  
  Purchase #2 $217.89   13.389%   $247.0633   $247.06   $247.05   $247.10  
  Purchase #3 $237.40   11.456%   $264.5965   $264.60   $264.60   $264.60  
  Purchase #4 $57.33   11.158%   $63.7269   $63.73   $63.75   $63.70  
  Purchase #5 $38.80   4.510%   $40.5499   $40.55   $40.55   $40.50  
  Purchase #6 $36.28   4.799%   $38.0211   $38.02   $38.00   $38.00  
  Purchase #7 $213.96   7.749%   $230.5398   $230.54   $230.55   $230.50  
  7 purchase totals = $920.36       $1,010.0239   $1,010.03   $1,010.05   $1,009.90