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 $57.84   7.211%   $62.0108   $62.01   $62.00   $62.00  
  Purchase #2 $44.64   7.783%   $48.1143   $48.11   $48.10   $48.10  
  Purchase #3 $176.74   11.381%   $196.8548   $196.85   $196.85   $196.90  
  Purchase #4 $161.77   13.473%   $183.5653   $183.57   $183.55   $183.60  
  Purchase #5 $141.34   5.453%   $149.0473   $149.05   $149.05   $149.00  
  Purchase #6 $197.31   10.644%   $218.3117   $218.31   $218.30   $218.30  
  Purchase #7 $226.44   11.838%   $253.246   $253.25   $253.25   $253.20  
  7 purchase totals = $1,006.08       $1,111.1502   $1,111.15   $1,111.10   $1,111.10