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 $211.89   10.732%   $234.63   $234.63   $234.65   $234.60  
  Purchase #2 $84.87   3.588%   $87.9151   $87.92   $87.90   $87.90  
  Purchase #3 $31.28   9.179%   $34.1512   $34.15   $34.15   $34.20  
  Purchase #4 $107.69   3.248%   $111.1878   $111.19   $111.20   $111.20  
  Purchase #5 $119.98   10.694%   $132.8107   $132.81   $132.80   $132.80  
  Purchase #6 $230.68   10.324%   $254.4954   $254.50   $254.50   $254.50  
  Purchase #7 $92.58   6.730%   $98.8106   $98.81   $98.80   $98.80  
  7 purchase totals = $878.97       $954.0008   $954.01   $954.00   $954.00