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	$225.60	5.771%	$238.6194	$238.62	$238.60	$238.60
Purchase #2	$79.30	4.185%	$82.6187	$82.62	$82.60	$82.60
Purchase #3	$118.82	8.103%	$128.448	$128.45	$128.45	$128.40
Purchase #4	$167.94	11.615%	$187.4462	$187.45	$187.45	$187.40
Purchase #5	$19.69	12.716%	$22.1938	$22.19	$22.20	$22.20
Purchase #6	$232.28	4.373%	$242.4376	$242.44	$242.45	$242.40
Purchase #7	$175.72	4.362%	$183.3849	$183.38	$183.40	$183.40
7 purchase totals =	$1,019.35		$1,085.1486	$1,085.15	$1,085.15	$1,085.00