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 $40.87   9.255%   $44.6525   $44.65   $44.65   $44.70  
  Purchase #2 $96.79   9.851%   $106.3248   $106.32   $106.30   $106.30  
  Purchase #3 $165.90   6.165%   $176.1277   $176.13   $176.15   $176.10  
  Purchase #4 $195.92   7.549%   $210.71   $210.71   $210.70   $210.70  
  Purchase #5 $123.81   9.846%   $136.0003   $136.00   $136.00   $136.00  
  Purchase #6 $189.50   9.734%   $207.9459   $207.95   $207.95   $207.90  
  Purchase #7 $154.77   12.650%   $174.3484   $174.35   $174.35   $174.30  
  7 purchase totals = $967.56       $1,056.1096   $1,056.11   $1,056.10   $1,056.00