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	$57.82	7.766%	$62.3103	$62.31	$62.30	$62.30
Purchase #2	$186.31	13.161%	$210.8303	$210.83	$210.85	$210.80
Purchase #3	$22.47	10.632%	$24.859	$24.86	$24.85	$24.90
Purchase #4	$146.32	13.509%	$166.0864	$166.09	$166.10	$166.10
Purchase #5	$94.36	4.251%	$98.3712	$98.37	$98.35	$98.40
Purchase #6	$96.78	8.403%	$104.9124	$104.91	$104.90	$104.90
Purchase #7	$76.32	3.234%	$78.7882	$78.79	$78.80	$78.80
7 purchase totals =	$680.38		$746.1578	$746.16	$746.15	$746.20