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 $211.29   11.382%   $235.339   $235.34   $235.35   $235.30  
  Purchase #2 $183.40   12.622%   $206.5487   $206.55   $206.55   $206.50  
  Purchase #3 $24.89   11.556%   $27.7663   $27.77   $27.75   $27.80  
  Purchase #4 $52.72   11.869%   $58.9773   $58.98   $59.00   $59.00  
  Purchase #5 $221.37   11.232%   $246.2343   $246.23   $246.25   $246.20  
  Purchase #6 $155.89   3.661%   $161.5971   $161.60   $161.60   $161.60  
  Purchase #7 $213.80   11.276%   $237.9081   $237.91   $237.90   $237.90  
  7 purchase totals = $1,063.36       $1,174.3708   $1,174.38   $1,174.40   $1,174.30