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	$64.30	13.379%	$72.9027	$72.90	$72.90	$72.90
Purchase #2	$205.27	10.159%	$226.1234	$226.12	$226.10	$226.10
Purchase #3	$57.58	3.250%	$59.4514	$59.45	$59.45	$59.50
Purchase #4	$213.49	5.230%	$224.6555	$224.66	$224.65	$224.70
Purchase #5	$106.48	4.183%	$110.9341	$110.93	$110.95	$110.90
Purchase #6	$186.82	11.684%	$208.648	$208.65	$208.65	$208.60
Purchase #7	$37.74	6.365%	$40.1422	$40.14	$40.15	$40.10
7 purchase totals =	$871.68		$942.8573	$942.85	$942.85	$942.80