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 $233.67   4.507%   $244.2015   $244.20   $244.20   $244.20  
  Purchase #2 $167.33   13.335%   $189.6435   $189.64   $189.65   $189.60  
  Purchase #3 $188.98   13.414%   $214.3298   $214.33   $214.35   $214.30  
  Purchase #4 $22.26   10.633%   $24.6269   $24.63   $24.65   $24.60  
  Purchase #5 $43.99   4.735%   $46.0729   $46.07   $46.05   $46.10  
  Purchase #6 $203.80   3.543%   $211.0206   $211.02   $211.00   $211.00  
  Purchase #7 $250.81   10.508%   $277.1651   $277.17   $277.15   $277.20  
  7 purchase totals = $1,110.84       $1,207.0603   $1,207.06   $1,207.05   $1,207.00