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 $44.31   5.625%   $46.8024   $46.80   $46.80   $46.80  
  Purchase #2 $151.75   5.681%   $160.3709   $160.37   $160.35   $160.40  
  Purchase #3 $239.35   7.552%   $257.4257   $257.43   $257.45   $257.40  
  Purchase #4 $97.71   7.150%   $104.6963   $104.70   $104.70   $104.70  
  Purchase #5 $33.45   13.557%   $37.9848   $37.98   $38.00   $38.00  
  Purchase #6 $94.93   5.414%   $100.0695   $100.07   $100.05   $100.10  
  Purchase #7 $50.31   8.632%   $54.6528   $54.65   $54.65   $54.70  
  7 purchase totals = $711.81       $762.0024   $762.00   $762.00   $762.10