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	$140.76	7.208%	$150.906	$150.91	$150.90	$150.90
Purchase #2	$157.77	5.741%	$166.8276	$166.83	$166.85	$166.80
Purchase #3	$133.63	6.867%	$142.8064	$142.81	$142.80	$142.80
Purchase #4	$74.69	5.569%	$78.8495	$78.85	$78.85	$78.80
Purchase #5	$155.44	5.854%	$164.5395	$164.54	$164.55	$164.50
Purchase #6	$186.30	8.679%	$202.469	$202.47	$202.45	$202.50
Purchase #7	$191.65	7.238%	$205.5216	$205.52	$205.50	$205.50
7 purchase totals =	$1,040.24		$1,111.9196	$1,111.93	$1,111.90	$1,111.80