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 $187.57   10.734%   $207.7038   $207.70   $207.70   $207.70  
  Purchase #2 $64.62   11.757%   $72.2174   $72.22   $72.20   $72.20  
  Purchase #3 $59.29   7.295%   $63.6152   $63.62   $63.60   $63.60  
  Purchase #4 $182.76   9.796%   $200.6632   $200.66   $200.65   $200.70  
  Purchase #5 $44.32   8.106%   $47.9126   $47.91   $47.90   $47.90  
  Purchase #6 $171.61   7.221%   $184.002   $184.00   $184.00   $184.00  
  Purchase #7 $153.82   7.409%   $165.2165   $165.22   $165.20   $165.20  
  7 purchase totals = $863.99       $941.3307   $941.33   $941.25   $941.30