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	$82.53	9.797%	$90.6155	$90.62	$90.60	$90.60
Purchase #2	$163.76	3.668%	$169.7667	$169.77	$169.75	$169.80
Purchase #3	$157.28	4.770%	$164.7823	$164.78	$164.80	$164.80
Purchase #4	$153.61	8.753%	$167.0555	$167.06	$167.05	$167.10
Purchase #5	$83.86	8.150%	$90.6946	$90.69	$90.70	$90.70
Purchase #6	$221.32	6.352%	$235.3782	$235.38	$235.40	$235.40
Purchase #7	$202.91	11.422%	$226.0864	$226.09	$226.10	$226.10
7 purchase totals =	$1,065.27		$1,144.3792	$1,144.39	$1,144.40	$1,144.50