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	$183.47	8.429%	$198.9347	$198.93	$198.95	$198.90
Purchase #2	$100.65	10.836%	$111.5564	$111.56	$111.55	$111.60
Purchase #3	$176.82	10.271%	$194.9812	$194.98	$195.00	$195.00
Purchase #4	$200.77	6.849%	$214.5207	$214.52	$214.50	$214.50
Purchase #5	$232.63	4.263%	$242.547	$242.55	$242.55	$242.50
Purchase #6	$30.69	5.769%	$32.4605	$32.46	$32.45	$32.50
Purchase #7	$71.83	11.715%	$80.2449	$80.24	$80.25	$80.20
7 purchase totals =	$996.86		$1,075.2454	$1,075.24	$1,075.25	$1,075.20