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 $140.95   9.353%   $154.1331   $154.13   $154.15   $154.10  
  Purchase #2 $106.89   11.516%   $119.1995   $119.20   $119.20   $119.20  
  Purchase #3 $85.95   8.488%   $93.2454   $93.25   $93.25   $93.20  
  Purchase #4 $248.70   4.626%   $260.2049   $260.20   $260.20   $260.20  
  Purchase #5 $152.92   12.651%   $172.2659   $172.27   $172.25   $172.30  
  Purchase #6 $85.65   3.681%   $88.8028   $88.80   $88.80   $88.80  
  Purchase #7 $141.85   3.732%   $147.1438   $147.14   $147.15   $147.10  
  7 purchase totals = $962.91       $1,034.9954   $1,034.99   $1,035.00   $1,034.90