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 $207.53   8.370%   $224.9003   $224.90   $224.90   $224.90  
  Purchase #2 $95.80   7.241%   $102.7369   $102.74   $102.75   $102.70  
  Purchase #3 $80.82   11.515%   $90.1264   $90.13   $90.15   $90.10  
  Purchase #4 $59.58   8.529%   $64.6616   $64.66   $64.65   $64.70  
  Purchase #5 $131.82   3.459%   $136.3797   $136.38   $136.40   $136.40  
  Purchase #6 $223.62   4.361%   $233.3721   $233.37   $233.35   $233.40  
  Purchase #7 $217.41   12.734%   $245.095   $245.10   $245.10   $245.10  
  7 purchase totals = $1,016.58       $1,097.2720   $1,097.28   $1,097.30   $1,097.30