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 $211.42   10.303%   $233.2026   $233.20   $233.20   $233.20  
  Purchase #2 $54.88   10.539%   $60.6638   $60.66   $60.65   $60.70  
  Purchase #3 $234.71   4.806%   $245.9902   $245.99   $246.00   $246.00  
  Purchase #4 $125.94   4.602%   $131.7358   $131.74   $131.75   $131.70  
  Purchase #5 $185.69   12.300%   $208.5299   $208.53   $208.55   $208.50  
  Purchase #6 $182.73   10.557%   $202.0208   $202.02   $202.00   $202.00  
  Purchase #7 $90.65   3.491%   $93.8146   $93.81   $93.80   $93.80  
  7 purchase totals = $1,086.02       $1,175.9577   $1,175.95   $1,175.95   $1,175.90