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	$64.27	11.317%	$71.5434	$71.54	$71.55	$71.50
Purchase #2	$103.91	7.409%	$111.6087	$111.61	$111.60	$111.60
Purchase #3	$245.97	5.648%	$259.8624	$259.86	$259.85	$259.90
Purchase #4	$233.36	10.288%	$257.3681	$257.37	$257.35	$257.40
Purchase #5	$230.25	3.516%	$238.3456	$238.35	$238.35	$238.30
Purchase #6	$115.70	5.812%	$122.4245	$122.42	$122.40	$122.40
Purchase #7	$227.89	11.460%	$254.0062	$254.01	$254.00	$254.00
7 purchase totals =	$1,221.35		$1,315.1589	$1,315.16	$1,315.10	$1,315.10