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 $32.44   5.381%   $34.1856   $34.19   $34.20   $34.20  
  Purchase #2 $174.90   6.465%   $186.2073   $186.21   $186.20   $186.20  
  Purchase #3 $103.79   6.210%   $110.2354   $110.24   $110.25   $110.20  
  Purchase #4 $106.77   4.839%   $111.9366   $111.94   $111.95   $111.90  
  Purchase #5 $239.64   11.154%   $266.3694   $266.37   $266.35   $266.40  
  Purchase #6 $206.54   5.216%   $217.3131   $217.31   $217.30   $217.30  
  Purchase #7 $104.76   6.471%   $111.539   $111.54   $111.55   $111.50  
  7 purchase totals = $968.84       $1,037.7864   $1,037.80   $1,037.80   $1,037.70