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	$207.40	6.799%	$221.5011	$221.50	$221.50	$221.50
Purchase #2	$196.76	4.632%	$205.8739	$205.87	$205.85	$205.90
Purchase #3	$31.31	10.332%	$34.5449	$34.54	$34.55	$34.50
Purchase #4	$146.62	13.826%	$166.8917	$166.89	$166.90	$166.90
Purchase #5	$244.31	4.573%	$255.4823	$255.48	$255.50	$255.50
Purchase #6	$108.86	12.827%	$122.8235	$122.82	$122.80	$122.80
Purchase #7	$172.44	3.754%	$178.9134	$178.91	$178.90	$178.90
7 purchase totals =	$1,107.70		$1,186.0308	$1,186.01	$1,186.00	$1,186.00