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 $47.26   11.461%   $52.6765   $52.68   $52.70   $52.70  
  Purchase #2 $99.50   12.302%   $111.7405   $111.74   $111.75   $111.70  
  Purchase #3 $215.74   3.590%   $223.4851   $223.49   $223.50   $223.50  
  Purchase #4 $91.36   4.578%   $95.5425   $95.54   $95.55   $95.50  
  Purchase #5 $108.66   11.540%   $121.1994   $121.20   $121.20   $121.20  
  Purchase #6 $226.43   12.836%   $255.4946   $255.49   $255.50   $255.50  
  Purchase #7 $246.81   3.716%   $255.9815   $255.98   $256.00   $256.00  
  7 purchase totals = $1,035.76       $1,116.1201   $1,116.12   $1,116.20   $1,116.10