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 $53.58   13.309%   $60.711   $60.71   $60.70   $60.70  
  Purchase #2 $89.97   6.809%   $96.0961   $96.10   $96.10   $96.10  
  Purchase #3 $198.86   5.285%   $209.3698   $209.37   $209.35   $209.40  
  Purchase #4 $60.59   11.415%   $67.5063   $67.51   $67.50   $67.50  
  Purchase #5 $235.80   11.180%   $262.1624   $262.16   $262.15   $262.20  
  Purchase #6 $214.74   13.598%   $243.9403   $243.94   $243.95   $243.90  
  Purchase #7 $35.53   5.234%   $37.3896   $37.39   $37.40   $37.40  
  7 purchase totals = $889.07       $977.1755   $977.18   $977.15   $977.20