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	$237.97	10.801%	$263.6731	$263.67	$263.65	$263.70
Purchase #2	$59.76	4.363%	$62.3673	$62.37	$62.35	$62.40
Purchase #3	$221.92	3.633%	$229.9824	$229.98	$230.00	$230.00
Purchase #4	$38.26	4.734%	$40.0712	$40.07	$40.05	$40.10
Purchase #5	$32.42	10.385%	$35.7868	$35.79	$35.80	$35.80
Purchase #6	$83.97	6.683%	$89.5817	$89.58	$89.60	$89.60
Purchase #7	$175.37	4.834%	$183.8474	$183.85	$183.85	$183.80
7 purchase totals =	$849.67		$905.3099	$905.31	$905.30	$905.40