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 $201.46   11.316%   $224.2572   $224.26   $224.25   $224.30  
  Purchase #2 $185.62   9.677%   $203.5824   $203.58   $203.60   $203.60  
  Purchase #3 $136.81   13.607%   $155.4257   $155.43   $155.45   $155.40  
  Purchase #4 $62.29   3.239%   $64.3076   $64.31   $64.30   $64.30  
  Purchase #5 $206.53   4.804%   $216.4517   $216.45   $216.45   $216.50  
  Purchase #6 $29.27   4.280%   $30.5228   $30.52   $30.50   $30.50  
  Purchase #7 $211.44   6.123%   $224.3865   $224.39   $224.40   $224.40  
  7 purchase totals = $1,033.42       $1,118.9339   $1,118.94   $1,118.95   $1,119.00