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 $209.48   5.279%   $220.5384   $220.54   $220.55   $220.50  
  Purchase #2 $137.50   3.781%   $142.6989   $142.70   $142.70   $142.70  
  Purchase #3 $9.80   4.417%   $10.2329   $10.23   $10.25   $10.20  
  Purchase #4 $63.71   3.153%   $65.7188   $65.72   $65.70   $65.70  
  Purchase #5 $133.91   6.356%   $142.4213   $142.42   $142.40   $142.40  
  Purchase #6 $216.88   4.474%   $226.5832   $226.58   $226.60   $226.60  
  Purchase #7 $198.81   3.787%   $206.3389   $206.34   $206.35   $206.30  
  7 purchase totals = $970.09       $1,014.5324   $1,014.53   $1,014.55   $1,014.40