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 $207.51   3.851%   $215.5012   $215.50   $215.50   $215.50  
  Purchase #2 $32.91   6.319%   $34.9896   $34.99   $35.00   $35.00  
  Purchase #3 $65.98   11.769%   $73.7452   $73.75   $73.75   $73.70  
  Purchase #4 $73.62   5.221%   $77.4637   $77.46   $77.45   $77.50  
  Purchase #5 $128.44   10.276%   $141.6385   $141.64   $141.65   $141.60  
  Purchase #6 $191.97   5.845%   $203.1906   $203.19   $203.20   $203.20  
  Purchase #7 $143.50   3.515%   $148.544   $148.54   $148.55   $148.50  
  7 purchase totals = $843.93       $895.0728   $895.07   $895.10   $895.00