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	$222.57	8.765%	$242.0783	$242.08	$242.10	$242.10
Purchase #2	$178.42	7.339%	$191.5142	$191.51	$191.50	$191.50
Purchase #3	$237.98	7.330%	$255.4239	$255.42	$255.40	$255.40
Purchase #4	$18.67	4.242%	$19.462	$19.46	$19.45	$19.50
Purchase #5	$234.63	9.325%	$256.5092	$256.51	$256.50	$256.50
Purchase #6	$135.31	12.126%	$151.7177	$151.72	$151.70	$151.70
Purchase #7	$78.76	3.601%	$81.5961	$81.60	$81.60	$81.60
7 purchase totals =	$1,106.34		$1,198.3014	$1,198.30	$1,198.25	$1,198.30