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	$211.89	5.491%	$223.5249	$223.52	$223.50	$223.50
Purchase #2	$34.46	10.414%	$38.0487	$38.05	$38.05	$38.00
Purchase #3	$171.58	4.671%	$179.5945	$179.59	$179.60	$179.60
Purchase #4	$165.68	13.141%	$187.452	$187.45	$187.45	$187.50
Purchase #5	$215.91	10.130%	$237.7817	$237.78	$237.80	$237.80
Purchase #6	$185.71	10.681%	$205.5457	$205.55	$205.55	$205.50
Purchase #7	$109.38	8.454%	$118.627	$118.63	$118.65	$118.60
7 purchase totals =	$1,094.61		$1,190.5745	$1,190.57	$1,190.60	$1,190.50