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 $85.55   11.387%   $95.2916   $95.29   $95.30   $95.30  
  Purchase #2 $217.66   5.349%   $229.3026   $229.30   $229.30   $229.30  
  Purchase #3 $87.48   6.165%   $92.8731   $92.87   $92.85   $92.90  
  Purchase #4 $108.55   6.167%   $115.2443   $115.24   $115.25   $115.20  
  Purchase #5 $223.55   8.468%   $242.4802   $242.48   $242.50   $242.50  
  Purchase #6 $13.43   5.119%   $14.1175   $14.12   $14.10   $14.10  
  Purchase #7 $226.39   4.365%   $236.2719   $236.27   $236.25   $236.30  
  7 purchase totals = $962.61       $1,025.5812   $1,025.57   $1,025.55   $1,025.60