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 $44.86   5.220%   $47.2017   $47.20   $47.20   $47.20  
  Purchase #2 $181.64   10.609%   $200.9102   $200.91   $200.90   $200.90  
  Purchase #3 $98.60   10.391%   $108.8455   $108.85   $108.85   $108.80  
  Purchase #4 $5.89   7.870%   $6.3535   $6.35   $6.35   $6.40  
  Purchase #5 $161.94   9.145%   $176.7494   $176.75   $176.75   $176.70  
  Purchase #6 $157.63   9.568%   $172.712   $172.71   $172.70   $172.70  
  Purchase #7 $56.86   4.837%   $59.6103   $59.61   $59.60   $59.60  
  7 purchase totals = $707.42       $772.3826   $772.38   $772.35   $772.30