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	$188.55	13.793%	$214.5567	$214.56	$214.55	$214.60
Purchase #2	$225.74	5.641%	$238.474	$238.47	$238.45	$238.50
Purchase #3	$42.71	4.354%	$44.5696	$44.57	$44.55	$44.60
Purchase #4	$112.50	10.302%	$124.0898	$124.09	$124.10	$124.10
Purchase #5	$91.55	9.280%	$100.0458	$100.05	$100.05	$100.00
Purchase #6	$162.92	5.132%	$171.2811	$171.28	$171.30	$171.30
Purchase #7	$159.50	4.429%	$166.5643	$166.56	$166.55	$166.60
7 purchase totals =	$983.47		$1,059.5813	$1,059.58	$1,059.55	$1,059.70