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 $175.61   3.842%   $182.3569   $182.36   $182.35   $182.40  
  Purchase #2 $237.75   10.285%   $262.2026   $262.20   $262.20   $262.20  
  Purchase #3 $103.77   5.605%   $109.5863   $109.59   $109.60   $109.60  
  Purchase #4 $112.82   8.455%   $122.3589   $122.36   $122.35   $122.40  
  Purchase #5 $120.68   3.813%   $125.2815   $125.28   $125.30   $125.30  
  Purchase #6 $29.49   6.785%   $31.4909   $31.49   $31.50   $31.50  
  Purchase #7 $170.81   6.136%   $181.2909   $181.29   $181.30   $181.30  
  7 purchase totals = $950.93       $1,014.5680   $1,014.57   $1,014.60   $1,014.70