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 $32.59   7.350%   $34.9854   $34.99   $35.00   $35.00  
  Purchase #2 $247.87   7.134%   $265.553   $265.55   $265.55   $265.60  
  Purchase #3 $115.36   11.649%   $128.7983   $128.80   $128.80   $128.80  
  Purchase #4 $100.71   10.336%   $111.1194   $111.12   $111.10   $111.10  
  Purchase #5 $219.36   7.443%   $235.687   $235.69   $235.70   $235.70  
  Purchase #6 $29.81   5.549%   $31.4642   $31.46   $31.45   $31.50  
  Purchase #7 $148.98   4.457%   $155.62   $155.62   $155.60   $155.60  
  7 purchase totals = $894.68       $963.2273   $963.23   $963.20   $963.30