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 $224.93   8.410%   $243.8466   $243.85   $243.85   $243.80  
  Purchase #2 $65.96   8.857%   $71.8021   $71.80   $71.80   $71.80  
  Purchase #3 $244.60   9.136%   $266.9467   $266.95   $266.95   $266.90  
  Purchase #4 $208.66   9.789%   $229.0857   $229.09   $229.10   $229.10  
  Purchase #5 $51.40   8.428%   $55.732   $55.73   $55.75   $55.70  
  Purchase #6 $155.64   13.764%   $177.0623   $177.06   $177.05   $177.10  
  Purchase #7 $54.57   10.658%   $60.3861   $60.39   $60.40   $60.40  
  7 purchase totals = $1,005.76       $1,104.8615   $1,104.87   $1,104.90   $1,104.80