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 $84.59   11.629%   $94.427   $94.43   $94.45   $94.40  
  Purchase #2 $204.27   4.661%   $213.791   $213.79   $213.80   $213.80  
  Purchase #3 $163.86   13.562%   $186.0827   $186.08   $186.10   $186.10  
  Purchase #4 $65.58   6.427%   $69.7948   $69.79   $69.80   $69.80  
  Purchase #5 $250.62   8.688%   $272.3939   $272.39   $272.40   $272.40  
  Purchase #6 $133.49   7.640%   $143.6886   $143.69   $143.70   $143.70  
  Purchase #7 $224.57   9.715%   $246.387   $246.39   $246.40   $246.40  
  7 purchase totals = $1,126.98       $1,226.5650   $1,226.56   $1,226.65   $1,226.60