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 $125.83   6.652%   $134.2002   $134.20   $134.20   $134.20  
  Purchase #2 $221.38   8.106%   $239.3251   $239.33   $239.35   $239.30  
  Purchase #3 $140.48   3.267%   $145.0695   $145.07   $145.05   $145.10  
  Purchase #4 $148.46   9.569%   $162.6661   $162.67   $162.65   $162.70  
  Purchase #5 $197.67   7.652%   $212.7957   $212.80   $212.80   $212.80  
  Purchase #6 $98.91   6.519%   $105.3579   $105.36   $105.35   $105.40  
  Purchase #7 $142.96   6.742%   $152.5984   $152.60   $152.60   $152.60  
  7 purchase totals = $1,075.69       $1,152.0129   $1,152.03   $1,152.00   $1,152.10