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	$49.78	6.336%	$52.9341	$52.93	$52.95	$52.90
Purchase #2	$95.42	10.327%	$105.274	$105.27	$105.25	$105.30
Purchase #3	$161.71	6.336%	$171.9559	$171.96	$171.95	$172.00
Purchase #4	$110.62	9.340%	$120.9519	$120.95	$120.95	$121.00
Purchase #5	$103.31	8.346%	$111.9323	$111.93	$111.95	$111.90
Purchase #6	$25.70	4.681%	$26.903	$26.90	$26.90	$26.90
Purchase #7	$160.85	3.558%	$166.573	$166.57	$166.55	$166.60
7 purchase totals =	$707.39		$756.5242	$756.51	$756.50	$756.60