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 $56.86   9.669%   $62.3578   $62.36   $62.35   $62.40  
  Purchase #2 $220.50   11.853%   $246.6359   $246.64   $246.65   $246.60  
  Purchase #3 $84.60   8.155%   $91.4991   $91.50   $91.50   $91.50  
  Purchase #4 $242.69   7.178%   $260.1103   $260.11   $260.10   $260.10  
  Purchase #5 $11.59   9.227%   $12.6594   $12.66   $12.65   $12.70  
  Purchase #6 $215.46   7.854%   $232.3822   $232.38   $232.40   $232.40  
  Purchase #7 $215.83   12.183%   $242.1246   $242.12   $242.10   $242.10  
  7 purchase totals = $1,047.53       $1,147.7693   $1,147.77   $1,147.75   $1,147.80