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 $58.68   10.685%   $64.95   $64.95   $64.95   $65.00  
  Purchase #2 $250.79   8.131%   $271.1817   $271.18   $271.20   $271.20  
  Purchase #3 $216.36   5.680%   $228.6492   $228.65   $228.65   $228.60  
  Purchase #4 $55.84   10.220%   $61.5468   $61.55   $61.55   $61.50  
  Purchase #5 $228.52   6.335%   $242.9967   $243.00   $243.00   $243.00  
  Purchase #6 $146.51   5.405%   $154.4289   $154.43   $154.45   $154.40  
  Purchase #7 $162.91   13.164%   $184.3555   $184.36   $184.35   $184.40  
  7 purchase totals = $1,119.61       $1,208.1088   $1,208.12   $1,208.15   $1,208.10