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 $96.55   7.769%   $104.051   $104.05   $104.05   $104.10  
  Purchase #2 $246.94   6.668%   $263.406   $263.41   $263.40   $263.40  
  Purchase #3 $71.93   3.760%   $74.6346   $74.63   $74.65   $74.60  
  Purchase #4 $214.77   13.296%   $243.3258   $243.33   $243.35   $243.30  
  Purchase #5 $9.49   4.476%   $9.9148   $9.91   $9.90   $9.90  
  Purchase #6 $250.40   8.647%   $272.0521   $272.05   $272.05   $272.10  
  Purchase #7 $82.71   12.574%   $93.11   $93.11   $93.10   $93.10  
  7 purchase totals = $972.79       $1,060.4943   $1,060.49   $1,060.50   $1,060.50