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	$105.31	6.342%	$111.9888	$111.99	$112.00	$112.00
Purchase #2	$11.52	7.847%	$12.424	$12.42	$12.40	$12.40
Purchase #3	$226.61	8.354%	$245.541	$245.54	$245.55	$245.50
Purchase #4	$83.65	6.187%	$88.8254	$88.83	$88.85	$88.80
Purchase #5	$180.45	6.168%	$191.5802	$191.58	$191.60	$191.60
Purchase #6	$191.62	9.288%	$209.4177	$209.42	$209.40	$209.40
Purchase #7	$69.36	12.823%	$78.254	$78.25	$78.25	$78.30
7 purchase totals =	$868.52		$938.0311	$938.03	$938.05	$938.00