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 $43.35   3.622%   $44.9201   $44.92   $44.90   $44.90  
  Purchase #2 $218.93   7.626%   $235.6256   $235.63   $235.65   $235.60  
  Purchase #3 $88.74   3.386%   $91.7447   $91.74   $91.75   $91.70  
  Purchase #4 $53.64   5.552%   $56.6181   $56.62   $56.60   $56.60  
  Purchase #5 $246.77   4.867%   $258.7803   $258.78   $258.80   $258.80  
  Purchase #6 $109.52   13.296%   $124.0818   $124.08   $124.10   $124.10  
  Purchase #7 $116.29   7.241%   $124.7106   $124.71   $124.70   $124.70  
  7 purchase totals = $877.24       $936.4812   $936.48   $936.50   $936.40