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	$136.66	10.567%	$151.1009	$151.10	$151.10	$151.10
Purchase #2	$227.77	4.821%	$238.7508	$238.75	$238.75	$238.80
Purchase #3	$157.36	9.669%	$172.5751	$172.58	$172.60	$172.60
Purchase #4	$102.73	9.757%	$112.7534	$112.75	$112.75	$112.80
Purchase #5	$150.96	5.608%	$159.4258	$159.43	$159.45	$159.40
Purchase #6	$48.63	12.567%	$54.7413	$54.74	$54.75	$54.70
Purchase #7	$185.86	13.308%	$210.5942	$210.59	$210.60	$210.60
7 purchase totals =	$1,009.97		$1,099.9415	$1,099.94	$1,100.00	$1,100.00