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 $66.87   10.121%   $73.6379   $73.64   $73.65   $73.60  
  Purchase #2 $12.44   5.275%   $13.0962   $13.10   $13.10   $13.10  
  Purchase #3 $31.75   10.380%   $35.0457   $35.05   $35.05   $35.00  
  Purchase #4 $134.83   10.649%   $149.188   $149.19   $149.20   $149.20  
  Purchase #5 $244.85   8.350%   $265.295   $265.30   $265.30   $265.30  
  Purchase #6 $162.59   11.612%   $181.47   $181.47   $181.45   $181.50  
  Purchase #7 $48.42   5.853%   $51.254   $51.25   $51.25   $51.30  
  7 purchase totals = $701.75       $768.9868   $769.00   $769.00   $769.00