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 $61.74   13.305%   $69.9545   $69.95   $69.95   $70.00  
  Purchase #2 $84.73   13.392%   $96.077   $96.08   $96.10   $96.10  
  Purchase #3 $48.27   4.717%   $50.5469   $50.55   $50.55   $50.50  
  Purchase #4 $57.71   7.519%   $62.0492   $62.05   $62.05   $62.00  
  Purchase #5 $156.49   4.237%   $163.1205   $163.12   $163.10   $163.10  
  Purchase #6 $79.40   4.749%   $83.1707   $83.17   $83.15   $83.20  
  Purchase #7 $46.97   7.844%   $50.6543   $50.65   $50.65   $50.70  
  7 purchase totals = $535.31       $575.5731   $575.57   $575.55   $575.60