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	$86.36	5.473%	$91.0865	$91.09	$91.10	$91.10
Purchase #2	$8.27	10.723%	$9.1568	$9.16	$9.15	$9.20
Purchase #3	$99.61	11.828%	$111.3919	$111.39	$111.40	$111.40
Purchase #4	$184.72	11.149%	$205.3144	$205.31	$205.30	$205.30
Purchase #5	$43.27	12.727%	$48.777	$48.78	$48.80	$48.80
Purchase #6	$206.55	7.648%	$222.3469	$222.35	$222.35	$222.30
Purchase #7	$212.56	4.535%	$222.1996	$222.20	$222.20	$222.20
7 purchase totals =	$841.34		$910.2731	$910.28	$910.30	$910.30