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	$202.58	5.444%	$213.6085	$213.61	$213.60	$213.60
Purchase #2	$105.98	13.536%	$120.3255	$120.33	$120.35	$120.30
Purchase #3	$194.31	8.779%	$211.3685	$211.37	$211.35	$211.40
Purchase #4	$226.63	13.347%	$256.8783	$256.88	$256.90	$256.90
Purchase #5	$156.96	10.162%	$172.9103	$172.91	$172.90	$172.90
Purchase #6	$127.83	3.618%	$132.4549	$132.45	$132.45	$132.50
Purchase #7	$37.46	9.395%	$40.9794	$40.98	$41.00	$41.00
7 purchase totals =	$1,051.75		$1,148.5254	$1,148.53	$1,148.55	$1,148.60