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	$142.76	6.108%	$151.4798	$151.48	$151.50	$151.50
Purchase #2	$12.75	6.688%	$13.6027	$13.60	$13.60	$13.60
Purchase #3	$225.25	4.611%	$235.6363	$235.64	$235.65	$235.60
Purchase #4	$47.96	13.547%	$54.4571	$54.46	$54.45	$54.50
Purchase #5	$164.75	4.226%	$171.7123	$171.71	$171.70	$171.70
Purchase #6	$87.28	13.628%	$99.1745	$99.17	$99.15	$99.20
Purchase #7	$212.94	12.409%	$239.3637	$239.36	$239.35	$239.40
7 purchase totals =	$893.69		$965.4264	$965.42	$965.40	$965.50