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 $212.75   7.293%   $228.2659   $228.27   $228.25   $228.30  
  Purchase #2 $195.83   3.767%   $203.2069   $203.21   $203.20   $203.20  
  Purchase #3 $187.58   3.237%   $193.652   $193.65   $193.65   $193.70  
  Purchase #4 $89.80   5.574%   $94.8055   $94.81   $94.80   $94.80  
  Purchase #5 $23.28   4.751%   $24.386   $24.39   $24.40   $24.40  
  Purchase #6 $154.69   5.422%   $163.0773   $163.08   $163.10   $163.10  
  Purchase #7 $181.67   3.870%   $188.7006   $188.70   $188.70   $188.70  
  7 purchase totals = $1,045.60       $1,096.0942   $1,096.11   $1,096.10   $1,096.20