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 $56.29   10.658%   $62.2894   $62.29   $62.30   $62.30  
  Purchase #2 $229.42   13.382%   $260.121   $260.12   $260.10   $260.10  
  Purchase #3 $212.68   13.712%   $241.8427   $241.84   $241.85   $241.80  
  Purchase #4 $41.48   9.656%   $45.4853   $45.49   $45.50   $45.50  
  Purchase #5 $184.70   13.292%   $209.2503   $209.25   $209.25   $209.30  
  Purchase #6 $212.36   10.195%   $234.0101   $234.01   $234.00   $234.00  
  Purchase #7 $14.59   3.509%   $15.102   $15.10   $15.10   $15.10  
  7 purchase totals = $951.52       $1,068.1008   $1,068.10   $1,068.10   $1,068.10