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 $228.95   5.701%   $242.0024   $242.00   $242.00   $242.00  
  Purchase #2 $216.58   5.239%   $227.9266   $227.93   $227.95   $227.90  
  Purchase #3 $67.29   10.289%   $74.2135   $74.21   $74.20   $74.20  
  Purchase #4 $94.64   6.516%   $100.8067   $100.81   $100.80   $100.80  
  Purchase #5 $165.74   3.551%   $171.6254   $171.63   $171.65   $171.60  
  Purchase #6 $182.28   6.476%   $194.0845   $194.08   $194.10   $194.10  
  Purchase #7 $164.91   10.810%   $182.7368   $182.74   $182.75   $182.70  
  7 purchase totals = $1,120.39       $1,193.3959   $1,193.40   $1,193.45   $1,193.30