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 $116.59   7.731%   $125.6036   $125.60   $125.60   $125.60  
  Purchase #2 $117.89   10.852%   $130.6834   $130.68   $130.70   $130.70  
  Purchase #3 $155.35   3.387%   $160.6117   $160.61   $160.60   $160.60  
  Purchase #4 $126.83   4.418%   $132.4333   $132.43   $132.45   $132.40  
  Purchase #5 $199.29   3.110%   $205.4879   $205.49   $205.50   $205.50  
  Purchase #6 $124.99   10.304%   $137.869   $137.87   $137.85   $137.90  
  Purchase #7 $106.46   9.782%   $116.8739   $116.87   $116.85   $116.90  
  7 purchase totals = $947.40       $1,009.5628   $1,009.55   $1,009.55   $1,009.60