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	$104.46	6.630%	$111.3857	$111.39	$111.40	$111.40
Purchase #2	$187.72	11.111%	$208.5776	$208.58	$208.60	$208.60
Purchase #3	$222.78	8.749%	$242.271	$242.27	$242.25	$242.30
Purchase #4	$151.91	10.398%	$167.7056	$167.71	$167.70	$167.70
Purchase #5	$222.78	9.225%	$243.3315	$243.33	$243.35	$243.30
Purchase #6	$208.93	8.794%	$227.3033	$227.30	$227.30	$227.30
Purchase #7	$247.94	7.364%	$266.1983	$266.20	$266.20	$266.20
7 purchase totals =	$1,346.52		$1,466.7730	$1,466.78	$1,466.80	$1,466.80