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 $87.36   9.535%   $95.6898   $95.69   $95.70   $95.70  
  Purchase #2 $153.65   6.836%   $164.1535   $164.15   $164.15   $164.20  
  Purchase #3 $61.26   3.320%   $63.2938   $63.29   $63.30   $63.30  
  Purchase #4 $129.40   4.261%   $134.9137   $134.91   $134.90   $134.90  
  Purchase #5 $24.53   10.872%   $27.1969   $27.20   $27.20   $27.20  
  Purchase #6 $186.75   11.545%   $208.3103   $208.31   $208.30   $208.30  
  Purchase #7 $129.26   11.251%   $143.803   $143.80   $143.80   $143.80  
  7 purchase totals = $772.21       $837.3610   $837.35   $837.35   $837.40