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	$214.65	3.593%	$222.3624	$222.36	$222.35	$222.40
Purchase #2	$128.84	10.296%	$142.1054	$142.11	$142.10	$142.10
Purchase #3	$104.66	13.534%	$118.8247	$118.82	$118.80	$118.80
Purchase #4	$31.41	3.821%	$32.6102	$32.61	$32.60	$32.60
Purchase #5	$10.39	9.777%	$11.4058	$11.41	$11.40	$11.40
Purchase #6	$118.64	10.482%	$131.0758	$131.08	$131.10	$131.10
Purchase #7	$69.44	7.216%	$74.4508	$74.45	$74.45	$74.50
7 purchase totals =	$678.03		$732.8351	$732.84	$732.80	$732.90