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 $53.94   9.335%   $58.9753   $58.98   $59.00   $59.00  
  Purchase #2 $170.91   8.679%   $185.7433   $185.74   $185.75   $185.70  
  Purchase #3 $222.78   7.793%   $240.1412   $240.14   $240.15   $240.10  
  Purchase #4 $58.61   11.613%   $65.4164   $65.42   $65.40   $65.40  
  Purchase #5 $116.73   6.678%   $124.5252   $124.53   $124.55   $124.50  
  Purchase #6 $194.35   6.128%   $206.2598   $206.26   $206.25   $206.30  
  Purchase #7 $245.92   11.358%   $273.8516   $273.85   $273.85   $273.90  
  7 purchase totals = $1,063.24       $1,154.9128   $1,154.92   $1,154.95   $1,154.90