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 $62.45   11.419%   $69.5812   $69.58   $69.60   $69.60  
  Purchase #2 $239.53   3.500%   $247.9136   $247.91   $247.90   $247.90  
  Purchase #3 $161.84   8.220%   $175.1432   $175.14   $175.15   $175.10  
  Purchase #4 $16.85   13.339%   $19.0976   $19.10   $19.10   $19.10  
  Purchase #5 $154.93   7.453%   $166.4769   $166.48   $166.50   $166.50  
  Purchase #6 $249.59   5.377%   $263.0105   $263.01   $263.00   $263.00  
  Purchase #7 $212.55   8.557%   $230.7379   $230.74   $230.75   $230.70  
  7 purchase totals = $1,097.74       $1,171.9609   $1,171.96   $1,172.00   $1,171.90