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	$100.81	13.166%	$114.0826	$114.08	$114.10	$114.10
Purchase #2	$138.83	3.324%	$143.4447	$143.44	$143.45	$143.40
Purchase #3	$29.59	13.620%	$33.6202	$33.62	$33.60	$33.60
Purchase #4	$111.98	7.471%	$120.346	$120.35	$120.35	$120.30
Purchase #5	$69.69	12.199%	$78.1915	$78.19	$78.20	$78.20
Purchase #6	$107.25	4.222%	$111.7781	$111.78	$111.80	$111.80
Purchase #7	$27.73	11.803%	$31.003	$31.00	$31.00	$31.00
7 purchase totals =	$585.88		$632.4661	$632.46	$632.50	$632.40