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 $151.94   8.606%   $165.016   $165.02   $165.00   $165.00  
  Purchase #2 $170.66   3.629%   $176.8533   $176.85   $176.85   $176.90  
  Purchase #3 $84.98   8.704%   $92.3767   $92.38   $92.40   $92.40  
  Purchase #4 $207.46   5.584%   $219.0446   $219.04   $219.05   $219.00  
  Purchase #5 $134.27   5.671%   $141.8845   $141.88   $141.90   $141.90  
  Purchase #6 $162.70   10.749%   $180.1886   $180.19   $180.20   $180.20  
  Purchase #7 $115.66   4.228%   $120.5501   $120.55   $120.55   $120.60  
  7 purchase totals = $1,027.67       $1,095.9138   $1,095.91   $1,095.95   $1,096.00