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	$132.63	7.606%	$142.7178	$142.72	$142.70	$142.70
Purchase #2	$152.46	12.150%	$170.9839	$170.98	$171.00	$171.00
Purchase #3	$207.53	7.755%	$223.624	$223.62	$223.60	$223.60
Purchase #4	$41.54	4.176%	$43.2747	$43.27	$43.25	$43.30
Purchase #5	$213.75	5.496%	$225.4977	$225.50	$225.50	$225.50
Purchase #6	$53.28	3.159%	$54.9631	$54.96	$54.95	$55.00
Purchase #7	$161.70	6.826%	$172.7376	$172.74	$172.75	$172.70
7 purchase totals =	$962.89		$1,033.7988	$1,033.79	$1,033.75	$1,033.80