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	$78.62	4.396%	$82.0761	$82.08	$82.10	$82.10
Purchase #2	$111.90	11.834%	$125.1422	$125.14	$125.15	$125.10
Purchase #3	$167.72	6.442%	$178.5245	$178.52	$178.50	$178.50
Purchase #4	$82.82	12.542%	$93.2073	$93.21	$93.20	$93.20
Purchase #5	$143.26	4.301%	$149.4216	$149.42	$149.40	$149.40
Purchase #6	$99.98	3.570%	$103.5493	$103.55	$103.55	$103.50
Purchase #7	$102.64	9.793%	$112.6915	$112.69	$112.70	$112.70
7 purchase totals =	$786.94		$844.6125	$844.61	$844.60	$844.50