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 $58.92   3.664%   $61.0788   $61.08   $61.10   $61.10  
  Purchase #2 $148.54   7.509%   $159.6939   $159.69   $159.70   $159.70  
  Purchase #3 $212.65   3.248%   $219.5569   $219.56   $219.55   $219.60  
  Purchase #4 $244.88   6.629%   $261.1131   $261.11   $261.10   $261.10  
  Purchase #5 $214.48   10.563%   $237.1355   $237.14   $237.15   $237.10  
  Purchase #6 $211.60   11.764%   $236.4926   $236.49   $236.50   $236.50  
  Purchase #7 $229.99   9.323%   $251.432   $251.43   $251.45   $251.40  
  7 purchase totals = $1,321.06       $1,426.5028   $1,426.50   $1,426.55   $1,426.50