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 $87.31   12.183%   $97.947   $97.95   $97.95   $97.90  
  Purchase #2 $217.82   6.727%   $232.4728   $232.47   $232.45   $232.50  
  Purchase #3 $228.37   11.188%   $253.92   $253.92   $253.90   $253.90  
  Purchase #4 $205.88   4.522%   $215.1899   $215.19   $215.20   $215.20  
  Purchase #5 $177.74   4.816%   $186.3   $186.30   $186.30   $186.30  
  Purchase #6 $199.78   13.405%   $226.5605   $226.56   $226.55   $226.60  
  Purchase #7 $170.44   8.164%   $184.3547   $184.35   $184.35   $184.40  
  7 purchase totals = $1,287.34       $1,396.7449   $1,396.74   $1,396.70   $1,396.80