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	$192.52	5.853%	$203.7882	$203.79	$203.80	$203.80
Purchase #2	$67.94	6.271%	$72.2005	$72.20	$72.20	$72.20
Purchase #3	$226.84	12.759%	$255.7825	$255.78	$255.80	$255.80
Purchase #4	$234.50	8.835%	$255.2181	$255.22	$255.20	$255.20
Purchase #5	$53.94	13.249%	$61.0865	$61.09	$61.10	$61.10
Purchase #6	$218.75	8.755%	$237.9016	$237.90	$237.90	$237.90
Purchase #7	$45.36	12.140%	$50.8667	$50.87	$50.85	$50.90
7 purchase totals =	$1,039.85		$1,136.8441	$1,136.85	$1,136.85	$1,136.90