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 $181.56   7.498%   $195.1734   $195.17   $195.15   $195.20  
  Purchase #2 $70.93   4.638%   $74.2197   $74.22   $74.20   $74.20  
  Purchase #3 $178.86   13.270%   $202.5947   $202.59   $202.60   $202.60  
  Purchase #4 $155.62   11.774%   $173.9427   $173.94   $173.95   $173.90  
  Purchase #5 $207.87   12.120%   $233.0638   $233.06   $233.05   $233.10  
  Purchase #6 $206.36   10.249%   $227.5098   $227.51   $227.50   $227.50  
  Purchase #7 $196.45   8.536%   $213.219   $213.22   $213.20   $213.20  
  7 purchase totals = $1,197.65       $1,319.7231   $1,319.71   $1,319.65   $1,319.70