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 $55.25   11.616%   $61.6678   $61.67   $61.65   $61.70  
  Purchase #2 $195.39   7.543%   $210.1283   $210.13   $210.15   $210.10  
  Purchase #3 $145.37   8.235%   $157.3412   $157.34   $157.35   $157.30  
  Purchase #4 $108.94   5.630%   $115.0733   $115.07   $115.05   $115.10  
  Purchase #5 $107.36   3.193%   $110.788   $110.79   $110.80   $110.80  
  Purchase #6 $223.84   12.328%   $251.435   $251.44   $251.45   $251.40  
  Purchase #7 $60.28   3.837%   $62.5929   $62.59   $62.60   $62.60  
  7 purchase totals = $896.43       $969.0265   $969.03   $969.05   $969.00