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	$138.31	9.575%	$151.5532	$151.55	$151.55	$151.60
Purchase #2	$85.86	4.613%	$89.8207	$89.82	$89.80	$89.80
Purchase #3	$240.31	10.873%	$266.4389	$266.44	$266.45	$266.40
Purchase #4	$242.40	7.540%	$260.677	$260.68	$260.70	$260.70
Purchase #5	$237.41	7.562%	$255.3629	$255.36	$255.35	$255.40
Purchase #6	$69.94	7.715%	$75.3359	$75.34	$75.35	$75.30
Purchase #7	$103.70	7.850%	$111.8405	$111.84	$111.85	$111.80
7 purchase totals =	$1,117.93		$1,211.0291	$1,211.03	$1,211.05	$1,211.00