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 $104.67   8.646%   $113.7198   $113.72   $113.70   $113.70  
  Purchase #2 $147.34   4.314%   $153.6962   $153.70   $153.70   $153.70  
  Purchase #3 $170.35   12.454%   $191.5654   $191.57   $191.55   $191.60  
  Purchase #4 $186.36   8.865%   $202.8808   $202.88   $202.90   $202.90  
  Purchase #5 $83.64   7.116%   $89.5918   $89.59   $89.60   $89.60  
  Purchase #6 $218.28   5.816%   $230.9752   $230.98   $231.00   $231.00  
  Purchase #7 $140.27   4.436%   $146.4924   $146.49   $146.50   $146.50  
  7 purchase totals = $1,050.91       $1,128.9216   $1,128.93   $1,128.95   $1,129.00