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 $87.47   10.625%   $96.7637   $96.76   $96.75   $96.80  
  Purchase #2 $100.61   3.685%   $104.3175   $104.32   $104.30   $104.30  
  Purchase #3 $87.64   8.537%   $95.1218   $95.12   $95.10   $95.10  
  Purchase #4 $222.48   11.217%   $247.4356   $247.44   $247.45   $247.40  
  Purchase #5 $56.59   11.141%   $62.8947   $62.89   $62.90   $62.90  
  Purchase #6 $126.77   5.794%   $134.1151   $134.12   $134.10   $134.10  
  Purchase #7 $192.73   6.171%   $204.6234   $204.62   $204.60   $204.60  
  7 purchase totals = $874.29       $945.2718   $945.27   $945.20   $945.20