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 $46.50   13.312%   $52.6901   $52.69   $52.70   $52.70  
  Purchase #2 $57.68   8.122%   $62.3648   $62.36   $62.35   $62.40  
  Purchase #3 $165.81   7.292%   $177.9009   $177.90   $177.90   $177.90  
  Purchase #4 $166.91   3.408%   $172.5983   $172.60   $172.60   $172.60  
  Purchase #5 $181.83   6.142%   $192.998   $193.00   $193.00   $193.00  
  Purchase #6 $183.63   6.539%   $195.6376   $195.64   $195.65   $195.60  
  Purchase #7 $214.26   9.176%   $233.9205   $233.92   $233.90   $233.90  
  7 purchase totals = $1,016.62       $1,088.1102   $1,088.11   $1,088.10   $1,088.10