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	$139.34	10.745%	$154.3121	$154.31	$154.30	$154.30
Purchase #2	$48.73	11.409%	$54.2896	$54.29	$54.30	$54.30
Purchase #3	$143.77	6.293%	$152.8174	$152.82	$152.80	$152.80
Purchase #4	$184.90	3.529%	$191.4251	$191.43	$191.45	$191.40
Purchase #5	$193.41	9.627%	$212.0296	$212.03	$212.05	$212.00
Purchase #6	$118.80	6.377%	$126.3759	$126.38	$126.40	$126.40
Purchase #7	$177.29	9.600%	$194.3098	$194.31	$194.30	$194.30
7 purchase totals =	$1,006.24		$1,085.5595	$1,085.57	$1,085.60	$1,085.50