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	$123.56	8.242%	$133.7438	$133.74	$133.75	$133.70
Purchase #2	$144.55	13.809%	$164.5109	$164.51	$164.50	$164.50
Purchase #3	$166.28	4.359%	$173.5281	$173.53	$173.55	$173.50
Purchase #4	$103.39	12.162%	$115.9643	$115.96	$115.95	$116.00
Purchase #5	$90.84	11.661%	$101.4329	$101.43	$101.45	$101.40
Purchase #6	$157.89	8.214%	$170.8591	$170.86	$170.85	$170.90
Purchase #7	$146.54	7.118%	$156.9707	$156.97	$156.95	$157.00
7 purchase totals =	$933.05		$1,017.0098	$1,017.00	$1,017.00	$1,017.00