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 $87.54   9.551%   $95.9009   $95.90   $95.90   $95.90  
  Purchase #2 $95.40   11.852%   $106.7068   $106.71   $106.70   $106.70  
  Purchase #3 $131.25   4.258%   $136.8386   $136.84   $136.85   $136.80  
  Purchase #4 $146.76   4.601%   $153.5124   $153.51   $153.50   $153.50  
  Purchase #5 $17.76   10.583%   $19.6395   $19.64   $19.65   $19.60  
  Purchase #6 $61.68   6.500%   $65.6892   $65.69   $65.70   $65.70  
  Purchase #7 $241.25   6.433%   $256.7696   $256.77   $256.75   $256.80  
  7 purchase totals = $781.64       $835.0570   $835.06   $835.05   $835.00