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 $173.49   5.760%   $183.483   $183.48   $183.50   $183.50  
  Purchase #2 $208.99   3.353%   $215.9974   $216.00   $216.00   $216.00  
  Purchase #3 $205.68   12.110%   $230.5878   $230.59   $230.60   $230.60  
  Purchase #4 $245.39   3.219%   $253.2891   $253.29   $253.30   $253.30  
  Purchase #5 $54.35   8.548%   $58.9958   $59.00   $59.00   $59.00  
  Purchase #6 $229.51   12.501%   $258.201   $258.20   $258.20   $258.20  
  Purchase #7 $48.55   4.858%   $50.9086   $50.91   $50.90   $50.90  
  7 purchase totals = $1,165.96       $1,251.4627   $1,251.47   $1,251.50   $1,251.50