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	$123.45	7.614%	$132.8495	$132.85	$132.85	$132.80
Purchase #2	$99.93	11.706%	$111.6278	$111.63	$111.65	$111.60
Purchase #3	$200.26	11.563%	$223.4161	$223.42	$223.40	$223.40
Purchase #4	$191.98	13.288%	$217.4903	$217.49	$217.50	$217.50
Purchase #5	$208.68	10.528%	$230.6498	$230.65	$230.65	$230.60
Purchase #6	$62.69	10.795%	$69.4574	$69.46	$69.45	$69.50
Purchase #7	$204.89	3.713%	$212.4976	$212.50	$212.50	$212.50
7 purchase totals =	$1,091.88		$1,197.9885	$1,198.00	$1,198.00	$1,197.90