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	$209.49	10.300%	$231.0675	$231.07	$231.05	$231.10
Purchase #2	$10.67	4.449%	$11.1447	$11.14	$11.15	$11.10
Purchase #3	$161.78	13.410%	$183.4747	$183.47	$183.45	$183.50
Purchase #4	$110.35	4.644%	$115.4747	$115.47	$115.45	$115.50
Purchase #5	$245.64	6.696%	$262.0881	$262.09	$262.10	$262.10
Purchase #6	$122.81	3.473%	$127.0752	$127.08	$127.10	$127.10
Purchase #7	$124.47	13.681%	$141.4987	$141.50	$141.50	$141.50
7 purchase totals =	$985.21		$1,071.8236	$1,071.82	$1,071.80	$1,071.90