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 $197.35   9.190%   $215.4865   $215.49   $215.50   $215.50  
  Purchase #2 $239.95   11.581%   $267.7386   $267.74   $267.75   $267.70  
  Purchase #3 $34.95   8.298%   $37.8502   $37.85   $37.85   $37.90  
  Purchase #4 $53.61   4.504%   $56.0246   $56.02   $56.00   $56.00  
  Purchase #5 $201.86   11.421%   $224.9144   $224.91   $224.90   $224.90  
  Purchase #6 $178.58   3.493%   $184.8178   $184.82   $184.80   $184.80  
  Purchase #7 $244.49   10.454%   $270.049   $270.05   $270.05   $270.00  
  7 purchase totals = $1,150.79       $1,256.8811   $1,256.88   $1,256.85   $1,256.80