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 $196.53   7.746%   $211.7532   $211.75   $211.75   $211.80  
  Purchase #2 $54.58   10.319%   $60.2121   $60.21   $60.20   $60.20  
  Purchase #3 $210.82   3.537%   $218.2767   $218.28   $218.30   $218.30  
  Purchase #4 $92.93   10.554%   $102.7378   $102.74   $102.75   $102.70  
  Purchase #5 $212.32   9.841%   $233.2144   $233.21   $233.20   $233.20  
  Purchase #6 $67.49   13.645%   $76.699   $76.70   $76.70   $76.70  
  Purchase #7 $51.64   7.315%   $55.4175   $55.42   $55.40   $55.40  
  7 purchase totals = $886.31       $958.3107   $958.31   $958.30   $958.30