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 $71.38   3.778%   $74.0767   $74.08   $74.10   $74.10  
  Purchase #2 $217.28   12.609%   $244.6768   $244.68   $244.70   $244.70  
  Purchase #3 $23.34   4.748%   $24.4482   $24.45   $24.45   $24.40  
  Purchase #4 $211.98   11.358%   $236.0567   $236.06   $236.05   $236.10  
  Purchase #5 $32.55   12.152%   $36.5055   $36.51   $36.50   $36.50  
  Purchase #6 $207.83   5.567%   $219.3999   $219.40   $219.40   $219.40  
  Purchase #7 $211.98   10.603%   $234.4562   $234.46   $234.45   $234.50  
  7 purchase totals = $976.34       $1,069.6200   $1,069.64   $1,069.65   $1,069.70