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 $71.56   5.679%   $75.6239   $75.62   $75.60   $75.60  
  Purchase #2 $106.57   8.133%   $115.2373   $115.24   $115.25   $115.20  
  Purchase #3 $167.88   4.381%   $175.2348   $175.23   $175.25   $175.20  
  Purchase #4 $171.38   8.219%   $185.4657   $185.47   $185.45   $185.50  
  Purchase #5 $43.84   6.158%   $46.5397   $46.54   $46.55   $46.50  
  Purchase #6 $243.85   3.572%   $252.5603   $252.56   $252.55   $252.60  
  Purchase #7 $81.38   7.189%   $87.2304   $87.23   $87.25   $87.20  
  7 purchase totals = $886.46       $937.8921   $937.89   $937.90   $937.80