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 $113.54   5.308%   $119.5667   $119.57   $119.55   $119.60  
  Purchase #2 $33.98   5.201%   $35.7473   $35.75   $35.75   $35.70  
  Purchase #3 $175.56   5.187%   $184.6663   $184.67   $184.65   $184.70  
  Purchase #4 $42.52   8.586%   $46.1708   $46.17   $46.15   $46.20  
  Purchase #5 $80.43   8.743%   $87.462   $87.46   $87.45   $87.50  
  Purchase #6 $134.87   13.538%   $153.1287   $153.13   $153.15   $153.10  
  Purchase #7 $84.77   6.172%   $90.002   $90.00   $90.00   $90.00  
  7 purchase totals = $665.67       $716.7438   $716.75   $716.70   $716.80