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 $57.36   13.448%   $65.0738   $65.07   $65.05   $65.10  
  Purchase #2 $186.25   5.446%   $196.3932   $196.39   $196.40   $196.40  
  Purchase #3 $204.44   3.283%   $211.1518   $211.15   $211.15   $211.20  
  Purchase #4 $142.46   9.346%   $155.7743   $155.77   $155.75   $155.80  
  Purchase #5 $159.60   10.164%   $175.8217   $175.82   $175.80   $175.80  
  Purchase #6 $243.98   4.136%   $254.071   $254.07   $254.05   $254.10  
  Purchase #7 $60.47   13.141%   $68.4164   $68.42   $68.40   $68.40  
  7 purchase totals = $1,054.56       $1,126.7022   $1,126.69   $1,126.60   $1,126.80