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 $69.78   3.159%   $71.9844   $71.98   $72.00   $72.00  
  Purchase #2 $216.27   8.643%   $234.9622   $234.96   $234.95   $235.00  
  Purchase #3 $214.31   6.642%   $228.5445   $228.54   $228.55   $228.50  
  Purchase #4 $217.57   7.219%   $233.2764   $233.28   $233.30   $233.30  
  Purchase #5 $138.37   5.554%   $146.0551   $146.06   $146.05   $146.10  
  Purchase #6 $236.73   12.160%   $265.5164   $265.52   $265.50   $265.50  
  Purchase #7 $232.85   6.670%   $248.3811   $248.38   $248.40   $248.40  
  7 purchase totals = $1,325.88       $1,428.7201   $1,428.72   $1,428.75   $1,428.80