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	$78.68	9.796%	$86.3875	$86.39	$86.40	$86.40
Purchase #2	$110.57	11.475%	$123.2579	$123.26	$123.25	$123.30
Purchase #3	$230.75	3.270%	$238.2955	$238.30	$238.30	$238.30
Purchase #4	$132.95	12.574%	$149.6671	$149.67	$149.65	$149.70
Purchase #5	$70.54	11.404%	$78.5844	$78.58	$78.60	$78.60
Purchase #6	$148.91	6.754%	$158.9674	$158.97	$158.95	$159.00
Purchase #7	$221.90	8.493%	$240.746	$240.75	$240.75	$240.70
7 purchase totals =	$994.30		$1,075.9058	$1,075.92	$1,075.90	$1,076.00