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 $63.71   11.185%   $70.836   $70.84   $70.85   $70.80  
  Purchase #2 $41.42   6.480%   $44.104   $44.10   $44.10   $44.10  
  Purchase #3 $156.81   3.587%   $162.4348   $162.43   $162.45   $162.40  
  Purchase #4 $222.67   3.421%   $230.2875   $230.29   $230.30   $230.30  
  Purchase #5 $246.27   7.743%   $265.3387   $265.34   $265.35   $265.30  
  Purchase #6 $138.82   3.407%   $143.5496   $143.55   $143.55   $143.50  
  Purchase #7 $178.30   13.611%   $202.5684   $202.57   $202.55   $202.60  
  7 purchase totals = $1,048.00       $1,119.1190   $1,119.12   $1,119.15   $1,119.00