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	$110.52	11.320%	$123.0309	$123.03	$123.05	$123.00
Purchase #2	$6.73	6.445%	$7.1637	$7.16	$7.15	$7.20
Purchase #3	$20.73	9.453%	$22.6896	$22.69	$22.70	$22.70
Purchase #4	$100.75	10.691%	$111.5212	$111.52	$111.50	$111.50
Purchase #5	$179.79	3.863%	$186.7353	$186.74	$186.75	$186.70
Purchase #6	$7.51	7.501%	$8.0733	$8.07	$8.05	$8.10
Purchase #7	$80.31	13.427%	$91.0932	$91.09	$91.10	$91.10
7 purchase totals =	$506.34		$550.3072	$550.30	$550.30	$550.30