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	$223.27	6.868%	$238.6042	$238.60	$238.60	$238.60
Purchase #2	$159.27	5.715%	$168.3723	$168.37	$168.35	$168.40
Purchase #3	$217.91	11.122%	$242.146	$242.15	$242.15	$242.10
Purchase #4	$56.27	11.574%	$62.7827	$62.78	$62.80	$62.80
Purchase #5	$94.53	4.630%	$98.9067	$98.91	$98.90	$98.90
Purchase #6	$51.93	12.743%	$58.5474	$58.55	$58.55	$58.50
Purchase #7	$250.78	8.313%	$271.6273	$271.63	$271.65	$271.60
7 purchase totals =	$1,053.96		$1,140.9866	$1,140.99	$1,141.00	$1,140.90