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 $208.28   3.328%   $215.2116   $215.21   $215.20   $215.20  
  Purchase #2 $244.46   5.193%   $257.1548   $257.15   $257.15   $257.20  
  Purchase #3 $49.37   5.362%   $52.0172   $52.02   $52.00   $52.00  
  Purchase #4 $230.33   9.247%   $251.6286   $251.63   $251.65   $251.60  
  Purchase #5 $243.35   6.634%   $259.4938   $259.49   $259.50   $259.50  
  Purchase #6 $231.66   13.817%   $263.6685   $263.67   $263.65   $263.70  
  Purchase #7 $190.95   8.107%   $206.4303   $206.43   $206.45   $206.40  
  7 purchase totals = $1,398.40       $1,505.6048   $1,505.60   $1,505.60   $1,505.60