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 $44.60   8.398%   $48.3455   $48.35   $48.35   $48.30  
  Purchase #2 $224.91   9.676%   $246.6723   $246.67   $246.65   $246.70  
  Purchase #3 $235.29   4.204%   $245.1816   $245.18   $245.20   $245.20  
  Purchase #4 $216.78   10.657%   $239.8822   $239.88   $239.90   $239.90  
  Purchase #5 $234.70   5.145%   $246.7753   $246.78   $246.80   $246.80  
  Purchase #6 $26.99   4.665%   $28.2491   $28.25   $28.25   $28.20  
  Purchase #7 $113.35   3.653%   $117.4907   $117.49   $117.50   $117.50  
  7 purchase totals = $1,096.62       $1,172.5967   $1,172.60   $1,172.65   $1,172.60