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 $202.72   6.527%   $215.9515   $215.95   $215.95   $216.00  
  Purchase #2 $95.29   5.670%   $100.6929   $100.69   $100.70   $100.70  
  Purchase #3 $111.56   9.862%   $122.562   $122.56   $122.55   $122.60  
  Purchase #4 $43.84   4.103%   $45.6388   $45.64   $45.65   $45.60  
  Purchase #5 $177.81   4.153%   $185.1944   $185.19   $185.20   $185.20  
  Purchase #6 $122.75   7.247%   $131.6457   $131.65   $131.65   $131.60  
  Purchase #7 $53.42   7.318%   $57.3293   $57.33   $57.35   $57.30  
  7 purchase totals = $807.39       $859.0146   $859.01   $859.05   $859.00