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 $209.26   10.858%   $231.9815   $231.98   $232.00   $232.00  
  Purchase #2 $80.83   5.183%   $85.0194   $85.02   $85.00   $85.00  
  Purchase #3 $70.97   11.309%   $78.996   $79.00   $79.00   $79.00  
  Purchase #4 $226.56   7.494%   $243.5384   $243.54   $243.55   $243.50  
  Purchase #5 $229.84   3.654%   $238.2384   $238.24   $238.25   $238.20  
  Purchase #6 $239.44   6.676%   $255.425   $255.43   $255.45   $255.40  
  Purchase #7 $27.62   4.252%   $28.7944   $28.79   $28.80   $28.80  
  7 purchase totals = $1,084.52       $1,161.9931   $1,162.00   $1,162.05   $1,161.90