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 $211.40   9.572%   $231.6352   $231.64   $231.65   $231.60  
  Purchase #2 $25.69   13.186%   $29.0775   $29.08   $29.10   $29.10  
  Purchase #3 $49.72   8.184%   $53.7891   $53.79   $53.80   $53.80  
  Purchase #4 $213.68   12.115%   $239.5673   $239.57   $239.55   $239.60  
  Purchase #5 $239.93   9.682%   $263.16   $263.16   $263.15   $263.20  
  Purchase #6 $71.25   9.761%   $78.2047   $78.20   $78.20   $78.20  
  Purchase #7 $108.25   9.451%   $118.4807   $118.48   $118.50   $118.50  
  7 purchase totals = $919.92       $1,013.9145   $1,013.92   $1,013.95   $1,014.00