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 $211.48   6.612%   $225.4631   $225.46   $225.45   $225.50  
  Purchase #2 $131.65   4.556%   $137.648   $137.65   $137.65   $137.60  
  Purchase #3 $26.96   8.415%   $29.2287   $29.23   $29.25   $29.20  
  Purchase #4 $50.76   6.716%   $54.169   $54.17   $54.15   $54.20  
  Purchase #5 $168.69   4.313%   $175.9656   $175.97   $175.95   $176.00  
  Purchase #6 $236.75   3.782%   $245.7039   $245.70   $245.70   $245.70  
  Purchase #7 $146.76   11.758%   $164.016   $164.02   $164.00   $164.00  
  7 purchase totals = $973.05       $1,032.1943   $1,032.20   $1,032.15   $1,032.20