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	$213.48	5.198%	$224.5767	$224.58	$224.60	$224.60
Purchase #2	$98.72	12.411%	$110.9721	$110.97	$110.95	$111.00
Purchase #3	$101.61	4.768%	$106.4548	$106.45	$106.45	$106.50
Purchase #4	$174.48	7.106%	$186.8785	$186.88	$186.90	$186.90
Purchase #5	$127.41	3.680%	$132.0987	$132.10	$132.10	$132.10
Purchase #6	$180.42	5.677%	$190.6624	$190.66	$190.65	$190.70
Purchase #7	$221.71	10.421%	$244.8144	$244.81	$244.80	$244.80
7 purchase totals =	$1,117.83		$1,196.4576	$1,196.45	$1,196.45	$1,196.60