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	$239.87	6.528%	$255.5287	$255.53	$255.55	$255.50
Purchase #2	$145.98	4.704%	$152.8469	$152.85	$152.85	$152.80
Purchase #3	$65.66	4.757%	$68.7834	$68.78	$68.80	$68.80
Purchase #4	$133.57	13.319%	$151.3602	$151.36	$151.35	$151.40
Purchase #5	$224.94	6.390%	$239.3137	$239.31	$239.30	$239.30
Purchase #6	$155.38	10.521%	$171.7275	$171.73	$171.75	$171.70
Purchase #7	$154.86	7.392%	$166.3073	$166.31	$166.30	$166.30
7 purchase totals =	$1,120.26		$1,205.8677	$1,205.87	$1,205.90	$1,205.80