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 $166.59   4.849%   $174.6679   $174.67   $174.65   $174.70  
  Purchase #2 $93.49   13.191%   $105.8223   $105.82   $105.80   $105.80  
  Purchase #3 $164.30   8.321%   $177.9714   $177.97   $177.95   $178.00  
  Purchase #4 $240.38   6.641%   $256.3436   $256.34   $256.35   $256.30  
  Purchase #5 $238.70   3.177%   $246.2835   $246.28   $246.30   $246.30  
  Purchase #6 $206.31   6.311%   $219.3302   $219.33   $219.35   $219.30  
  Purchase #7 $238.37   5.409%   $251.2634   $251.26   $251.25   $251.30  
  7 purchase totals = $1,348.14       $1,431.6823   $1,431.67   $1,431.65   $1,431.70