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 $162.51   3.179%   $167.6762   $167.68   $167.70   $167.70  
  Purchase #2 $168.99   12.652%   $190.3706   $190.37   $190.35   $190.40  
  Purchase #3 $67.85   8.484%   $73.6064   $73.61   $73.60   $73.60  
  Purchase #4 $94.55   13.150%   $106.9833   $106.98   $107.00   $107.00  
  Purchase #5 $141.58   3.203%   $146.1148   $146.11   $146.10   $146.10  
  Purchase #6 $48.91   6.821%   $52.2462   $52.25   $52.25   $52.20  
  Purchase #7 $14.39   9.196%   $15.7133   $15.71   $15.70   $15.70  
  7 purchase totals = $698.78       $752.7108   $752.71   $752.70   $752.70