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	$62.27	5.775%	$65.8661	$65.87	$65.85	$65.90
Purchase #2	$96.72	9.131%	$105.5515	$105.55	$105.55	$105.60
Purchase #3	$80.53	9.743%	$88.376	$88.38	$88.40	$88.40
Purchase #4	$235.92	10.467%	$260.6137	$260.61	$260.60	$260.60
Purchase #5	$238.58	5.846%	$252.5274	$252.53	$252.55	$252.50
Purchase #6	$186.42	10.577%	$206.1376	$206.14	$206.15	$206.10
Purchase #7	$37.67	7.305%	$40.4218	$40.42	$40.40	$40.40
7 purchase totals =	$938.11		$1,019.4941	$1,019.50	$1,019.50	$1,019.50