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	$223.50	6.537%	$238.1102	$238.11	$238.10	$238.10
Purchase #2	$124.97	5.744%	$132.1483	$132.15	$132.15	$132.10
Purchase #3	$119.54	11.109%	$132.8197	$132.82	$132.80	$132.80
Purchase #4	$238.50	11.339%	$265.5435	$265.54	$265.55	$265.50
Purchase #5	$36.29	5.467%	$38.274	$38.27	$38.25	$38.30
Purchase #6	$240.86	8.135%	$260.454	$260.45	$260.45	$260.50
Purchase #7	$105.25	12.683%	$118.5989	$118.60	$118.60	$118.60
7 purchase totals =	$1,088.91		$1,185.9486	$1,185.94	$1,185.90	$1,185.90