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 $214.65   9.279%   $234.5674   $234.57   $234.55   $234.60  
  Purchase #2 $228.67   10.845%   $253.4693   $253.47   $253.45   $253.50  
  Purchase #3 $122.37   10.680%   $135.4391   $135.44   $135.45   $135.40  
  Purchase #4 $205.37   6.365%   $218.4418   $218.44   $218.45   $218.40  
  Purchase #5 $234.94   4.597%   $245.7402   $245.74   $245.75   $245.70  
  Purchase #6 $172.81   7.367%   $185.5409   $185.54   $185.55   $185.50  
  Purchase #7 $191.80   5.422%   $202.1994   $202.20   $202.20   $202.20  
  7 purchase totals = $1,370.61       $1,475.3981   $1,475.40   $1,475.40   $1,475.30