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	$9.75	12.371%	$10.9562	$10.96	$10.95	$11.00
Purchase #2	$28.66	11.613%	$31.9883	$31.99	$32.00	$32.00
Purchase #3	$59.30	7.261%	$63.6058	$63.61	$63.60	$63.60
Purchase #4	$101.29	11.661%	$113.1014	$113.10	$113.10	$113.10
Purchase #5	$94.78	9.407%	$103.696	$103.70	$103.70	$103.70
Purchase #6	$86.59	3.162%	$89.328	$89.33	$89.35	$89.30
Purchase #7	$135.94	7.707%	$146.4169	$146.42	$146.40	$146.40
7 purchase totals =	$516.31		$559.0926	$559.11	$559.10	$559.10