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 $98.61   5.368%   $103.9034   $103.90   $103.90   $103.90  
  Purchase #2 $219.81   12.768%   $247.8753   $247.88   $247.90   $247.90  
  Purchase #3 $22.83   13.706%   $25.9591   $25.96   $25.95   $26.00  
  Purchase #4 $95.60   6.577%   $101.8876   $101.89   $101.90   $101.90  
  Purchase #5 $232.81   4.417%   $243.0932   $243.09   $243.10   $243.10  
  Purchase #6 $218.84   5.381%   $230.6158   $230.62   $230.60   $230.60  
  Purchase #7 $207.85   3.209%   $214.5199   $214.52   $214.50   $214.50  
  7 purchase totals = $1,096.35       $1,167.8543   $1,167.86   $1,167.85   $1,167.90