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	$238.28	9.192%	$260.1827	$260.18	$260.20	$260.20
Purchase #2	$215.28	6.547%	$229.3744	$229.37	$229.35	$229.40
Purchase #3	$192.51	3.298%	$198.859	$198.86	$198.85	$198.90
Purchase #4	$137.71	4.303%	$143.6357	$143.64	$143.65	$143.60
Purchase #5	$58.97	5.681%	$62.3201	$62.32	$62.30	$62.30
Purchase #6	$171.43	8.167%	$185.4307	$185.43	$185.45	$185.40
Purchase #7	$90.67	6.667%	$96.715	$96.72	$96.70	$96.70
7 purchase totals =	$1,104.85		$1,176.5176	$1,176.52	$1,176.50	$1,176.50