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 $41.68   4.378%   $43.5048   $43.50   $43.50   $43.50  
  Purchase #2 $217.99   3.498%   $225.6153   $225.62   $225.60   $225.60  
  Purchase #3 $165.87   3.533%   $171.7302   $171.73   $171.75   $171.70  
  Purchase #4 $218.76   11.611%   $244.1602   $244.16   $244.15   $244.20  
  Purchase #5 $113.89   4.228%   $118.7053   $118.71   $118.70   $118.70  
  Purchase #6 $222.45   3.523%   $230.2869   $230.29   $230.30   $230.30  
  Purchase #7 $194.53   8.388%   $210.8472   $210.85   $210.85   $210.80  
  7 purchase totals = $1,175.17       $1,244.8499   $1,244.86   $1,244.85   $1,244.80