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 $59.72   5.752%   $63.1551   $63.16   $63.15   $63.20  
  Purchase #2 $225.99   3.336%   $233.529   $233.53   $233.55   $233.50  
  Purchase #3 $191.50   3.535%   $198.2695   $198.27   $198.25   $198.30  
  Purchase #4 $167.27   3.531%   $173.1763   $173.18   $173.20   $173.20  
  Purchase #5 $69.69   10.648%   $77.1106   $77.11   $77.10   $77.10  
  Purchase #6 $209.43   4.568%   $218.9968   $219.00   $219.00   $219.00  
  Purchase #7 $134.49   13.836%   $153.098   $153.10   $153.10   $153.10  
  7 purchase totals = $1,058.09       $1,117.3353   $1,117.35   $1,117.35   $1,117.40