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	$63.98	11.850%	$71.5616	$71.56	$71.55	$71.60
Purchase #2	$171.62	4.174%	$178.7834	$178.78	$178.80	$178.80
Purchase #3	$173.28	8.138%	$187.3815	$187.38	$187.40	$187.40
Purchase #4	$217.74	12.332%	$244.5917	$244.59	$244.60	$244.60
Purchase #5	$237.77	13.225%	$269.2151	$269.22	$269.20	$269.20
Purchase #6	$49.46	13.229%	$56.0031	$56.00	$56.00	$56.00
Purchase #7	$155.35	10.556%	$171.7487	$171.75	$171.75	$171.70
7 purchase totals =	$1,069.20		$1,179.2851	$1,179.28	$1,179.30	$1,179.30