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	$227.37	4.851%	$238.3997	$238.40	$238.40	$238.40
Purchase #2	$119.51	3.156%	$123.2817	$123.28	$123.30	$123.30
Purchase #3	$108.99	4.530%	$113.9272	$113.93	$113.95	$113.90
Purchase #4	$210.76	6.168%	$223.7597	$223.76	$223.75	$223.80
Purchase #5	$111.45	9.436%	$121.9664	$121.97	$121.95	$122.00
Purchase #6	$156.86	6.737%	$167.4277	$167.43	$167.45	$167.40
Purchase #7	$123.83	6.207%	$131.5161	$131.52	$131.50	$131.50
7 purchase totals =	$1,058.77		$1,120.2785	$1,120.29	$1,120.30	$1,120.30