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 $55.68   10.511%   $61.5325   $61.53   $61.55   $61.50  
  Purchase #2 $205.61   4.742%   $215.36   $215.36   $215.35   $215.40  
  Purchase #3 $117.98   8.696%   $128.2395   $128.24   $128.25   $128.20  
  Purchase #4 $7.30   6.334%   $7.7624   $7.76   $7.75   $7.80  
  Purchase #5 $206.82   5.410%   $218.009   $218.01   $218.00   $218.00  
  Purchase #6 $178.29   6.389%   $189.6809   $189.68   $189.70   $189.70  
  Purchase #7 $212.59   10.537%   $234.9906   $234.99   $235.00   $235.00  
  7 purchase totals = $984.27       $1,055.5749   $1,055.57   $1,055.60   $1,055.60