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 $22.60   4.393%   $23.5928   $23.59   $23.60   $23.60  
  Purchase #2 $97.79   8.744%   $106.3408   $106.34   $106.35   $106.30  
  Purchase #3 $238.45   11.466%   $265.7907   $265.79   $265.80   $265.80  
  Purchase #4 $244.39   3.846%   $253.7892   $253.79   $253.80   $253.80  
  Purchase #5 $174.93   11.523%   $195.0872   $195.09   $195.10   $195.10  
  Purchase #6 $241.41   3.634%   $250.1828   $250.18   $250.20   $250.20  
  Purchase #7 $57.40   11.835%   $64.1933   $64.19   $64.20   $64.20  
  7 purchase totals = $1,076.97       $1,158.9768   $1,158.97   $1,159.05   $1,159.00