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 $147.98   9.589%   $162.1698   $162.17   $162.15   $162.20  
  Purchase #2 $181.60   9.269%   $198.4325   $198.43   $198.45   $198.40  
  Purchase #3 $69.48   3.532%   $71.934   $71.93   $71.95   $71.90  
  Purchase #4 $87.32   6.585%   $93.07   $93.07   $93.05   $93.10  
  Purchase #5 $77.36   5.531%   $81.6388   $81.64   $81.65   $81.60  
  Purchase #6 $11.81   11.711%   $13.1931   $13.19   $13.20   $13.20  
  Purchase #7 $127.38   3.520%   $131.8638   $131.86   $131.85   $131.90  
  7 purchase totals = $702.93       $752.3020   $752.29   $752.30   $752.30