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 $182.77   10.496%   $201.9535   $201.95   $201.95   $202.00  
  Purchase #2 $19.52   12.473%   $21.9547   $21.95   $21.95   $22.00  
  Purchase #3 $76.90   5.197%   $80.8965   $80.90   $80.90   $80.90  
  Purchase #4 $60.85   9.778%   $66.7999   $66.80   $66.80   $66.80  
  Purchase #5 $220.95   5.580%   $233.279   $233.28   $233.30   $233.30  
  Purchase #6 $10.44   11.667%   $11.658   $11.66   $11.65   $11.70  
  Purchase #7 $115.65   3.382%   $119.5613   $119.56   $119.55   $119.60  
  7 purchase totals = $687.08       $736.1029   $736.10   $736.10   $736.30