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 $200.96   4.596%   $210.1961   $210.20   $210.20   $210.20  
  Purchase #2 $236.93   12.255%   $265.9658   $265.97   $265.95   $266.00  
  Purchase #3 $56.66   5.128%   $59.5655   $59.57   $59.55   $59.60  
  Purchase #4 $116.75   3.393%   $120.7113   $120.71   $120.70   $120.70  
  Purchase #5 $216.47   4.497%   $226.2047   $226.20   $226.20   $226.20  
  Purchase #6 $107.45   13.550%   $122.0095   $122.01   $122.00   $122.00  
  Purchase #7 $108.92   11.729%   $121.6952   $121.70   $121.70   $121.70  
  7 purchase totals = $1,044.14       $1,126.3481   $1,126.36   $1,126.30   $1,126.40