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 $69.33   10.487%   $76.6006   $76.60   $76.60   $76.60  
  Purchase #2 $211.71   3.128%   $218.3323   $218.33   $218.35   $218.30  
  Purchase #3 $206.69   6.281%   $219.6722   $219.67   $219.65   $219.70  
  Purchase #4 $17.96   13.422%   $20.3706   $20.37   $20.35   $20.40  
  Purchase #5 $245.88   3.172%   $253.6793   $253.68   $253.70   $253.70  
  Purchase #6 $221.49   6.580%   $236.064   $236.06   $236.05   $236.10  
  Purchase #7 $159.70   8.868%   $173.8622   $173.86   $173.85   $173.90  
  7 purchase totals = $1,132.76       $1,198.5812   $1,198.57   $1,198.55   $1,198.70