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 $68.56   7.332%   $73.5868   $73.59   $73.60   $73.60  
  Purchase #2 $223.61   11.241%   $248.746   $248.75   $248.75   $248.70  
  Purchase #3 $231.37   5.265%   $243.5516   $243.55   $243.55   $243.60  
  Purchase #4 $149.77   5.694%   $158.2979   $158.30   $158.30   $158.30  
  Purchase #5 $231.26   10.747%   $256.1135   $256.11   $256.10   $256.10  
  Purchase #6 $132.99   6.392%   $141.4907   $141.49   $141.50   $141.50  
  Purchase #7 $27.47   13.417%   $31.1556   $31.16   $31.15   $31.20  
  7 purchase totals = $1,065.03       $1,152.9421   $1,152.95   $1,152.95   $1,153.00