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	$130.77	8.354%	$141.6945	$141.69	$141.70	$141.70
Purchase #2	$105.53	3.452%	$109.1729	$109.17	$109.15	$109.20
Purchase #3	$238.32	13.201%	$269.7806	$269.78	$269.80	$269.80
Purchase #4	$175.58	4.264%	$183.0667	$183.07	$183.05	$183.10
Purchase #5	$41.77	9.128%	$45.5828	$45.58	$45.60	$45.60
Purchase #6	$228.41	8.593%	$248.0373	$248.04	$248.05	$248.00
Purchase #7	$19.88	9.161%	$21.7012	$21.70	$21.70	$21.70
7 purchase totals =	$940.26		$1,019.0360	$1,019.03	$1,019.05	$1,019.10