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 $53.87   5.533%   $56.8506   $56.85   $56.85   $56.90  
  Purchase #2 $116.97   7.856%   $126.1592   $126.16   $126.15   $126.20  
  Purchase #3 $151.28   11.425%   $168.5637   $168.56   $168.55   $168.60  
  Purchase #4 $186.29   3.539%   $192.8828   $192.88   $192.90   $192.90  
  Purchase #5 $87.57   7.313%   $93.974   $93.97   $93.95   $94.00  
  Purchase #6 $207.72   4.248%   $216.5439   $216.54   $216.55   $216.50  
  Purchase #7 $204.72   5.370%   $215.7135   $215.71   $215.70   $215.70  
  7 purchase totals = $1,008.42       $1,070.6877   $1,070.67   $1,070.65   $1,070.80