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 $53.96   10.461%   $59.6048   $59.60   $59.60   $59.60  
  Purchase #2 $166.34   11.314%   $185.1597   $185.16   $185.15   $185.20  
  Purchase #3 $205.28   5.571%   $216.7161   $216.72   $216.70   $216.70  
  Purchase #4 $246.44   5.662%   $260.3934   $260.39   $260.40   $260.40  
  Purchase #5 $226.53   5.509%   $239.0095   $239.01   $239.00   $239.00  
  Purchase #6 $211.89   8.376%   $229.6379   $229.64   $229.65   $229.60  
  Purchase #7 $209.78   7.514%   $225.5429   $225.54   $225.55   $225.50  
  7 purchase totals = $1,320.22       $1,416.0643   $1,416.06   $1,416.05   $1,416.00