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	$164.68	10.839%	$182.5297	$182.53	$182.55	$182.50
Purchase #2	$183.72	10.775%	$203.5158	$203.52	$203.50	$203.50
Purchase #3	$122.99	6.618%	$131.1295	$131.13	$131.15	$131.10
Purchase #4	$51.27	6.224%	$54.461	$54.46	$54.45	$54.50
Purchase #5	$36.52	6.867%	$39.0278	$39.03	$39.05	$39.00
Purchase #6	$156.78	10.746%	$173.6276	$173.63	$173.65	$173.60
Purchase #7	$215.91	3.271%	$222.9724	$222.97	$222.95	$223.00
7 purchase totals =	$931.87		$1,007.2638	$1,007.27	$1,007.30	$1,007.20