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	$210.73	5.714%	$222.7711	$222.77	$222.75	$222.80
Purchase #2	$155.73	12.471%	$175.1511	$175.15	$175.15	$175.20
Purchase #3	$63.31	7.864%	$68.2887	$68.29	$68.30	$68.30
Purchase #4	$62.77	4.352%	$65.5018	$65.50	$65.50	$65.50
Purchase #5	$12.86	11.304%	$14.3137	$14.31	$14.30	$14.30
Purchase #6	$139.54	4.260%	$145.4844	$145.48	$145.50	$145.50
Purchase #7	$190.39	10.485%	$210.3524	$210.35	$210.35	$210.40
7 purchase totals =	$835.33		$901.8632	$901.85	$901.85	$902.00