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	$81.86	5.528%	$86.3852	$86.39	$86.40	$86.40
Purchase #2	$19.97	6.550%	$21.278	$21.28	$21.30	$21.30
Purchase #3	$105.31	12.320%	$118.2842	$118.28	$118.30	$118.30
Purchase #4	$158.25	5.614%	$167.1342	$167.13	$167.15	$167.10
Purchase #5	$82.62	6.222%	$87.7606	$87.76	$87.75	$87.80
Purchase #6	$148.60	4.266%	$154.9393	$154.94	$154.95	$154.90
Purchase #7	$166.43	3.380%	$172.0553	$172.06	$172.05	$172.10
7 purchase totals =	$763.04		$807.8368	$807.84	$807.90	$807.90