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	$112.59	13.634%	$127.9405	$127.94	$127.95	$127.90
Purchase #2	$116.27	6.253%	$123.5404	$123.54	$123.55	$123.50
Purchase #3	$196.49	10.133%	$216.4003	$216.40	$216.40	$216.40
Purchase #4	$172.72	4.604%	$180.672	$180.67	$180.65	$180.70
Purchase #5	$185.54	10.562%	$205.1367	$205.14	$205.15	$205.10
Purchase #6	$226.98	13.567%	$257.7744	$257.77	$257.75	$257.80
Purchase #7	$142.48	10.558%	$157.523	$157.52	$157.50	$157.50
7 purchase totals =	$1,153.07		$1,268.9873	$1,268.98	$1,268.95	$1,268.90