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	$175.57	6.699%	$187.3314	$187.33	$187.35	$187.30
Purchase #2	$238.90	3.276%	$246.7264	$246.73	$246.75	$246.70
Purchase #3	$103.56	8.654%	$112.5221	$112.52	$112.50	$112.50
Purchase #4	$42.68	13.754%	$48.5502	$48.55	$48.55	$48.60
Purchase #5	$100.91	4.734%	$105.6871	$105.69	$105.70	$105.70
Purchase #6	$178.96	3.461%	$185.1538	$185.15	$185.15	$185.20
Purchase #7	$210.82	4.152%	$219.5732	$219.57	$219.55	$219.60
7 purchase totals =	$1,051.40		$1,105.5442	$1,105.54	$1,105.55	$1,105.60