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 $118.97   5.278%   $125.2492   $125.25   $125.25   $125.20  
  Purchase #2 $10.81   9.199%   $11.8044   $11.80   $11.80   $11.80  
  Purchase #3 $177.38   8.178%   $191.8861   $191.89   $191.90   $191.90  
  Purchase #4 $212.60   12.594%   $239.3748   $239.37   $239.35   $239.40  
  Purchase #5 $162.82   5.448%   $171.6904   $171.69   $171.70   $171.70  
  Purchase #6 $219.32   5.288%   $230.9176   $230.92   $230.90   $230.90  
  Purchase #7 $101.95   10.136%   $112.2837   $112.28   $112.30   $112.30  
  7 purchase totals = $1,003.85       $1,083.2062   $1,083.20   $1,083.20   $1,083.20