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	$21.85	4.839%	$22.9073	$22.91	$22.90	$22.90
Purchase #2	$57.45	9.249%	$62.7636	$62.76	$62.75	$62.80
Purchase #3	$106.77	4.428%	$111.4978	$111.50	$111.50	$111.50
Purchase #4	$15.28	12.854%	$17.2441	$17.24	$17.25	$17.20
Purchase #5	$13.28	11.251%	$14.7741	$14.77	$14.75	$14.80
Purchase #6	$112.46	4.169%	$117.1485	$117.15	$117.15	$117.10
Purchase #7	$86.32	12.359%	$96.9883	$96.99	$97.00	$97.00
7 purchase totals =	$413.41		$443.3237	$443.32	$443.30	$443.30