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	$179.38	11.244%	$199.5495	$199.55	$199.55	$199.50
Purchase #2	$12.90	10.463%	$14.2497	$14.25	$14.25	$14.20
Purchase #3	$99.49	11.685%	$111.1154	$111.12	$111.10	$111.10
Purchase #4	$78.30	8.542%	$84.9884	$84.99	$85.00	$85.00
Purchase #5	$89.35	4.706%	$93.5548	$93.55	$93.55	$93.60
Purchase #6	$193.47	3.686%	$200.6013	$200.60	$200.60	$200.60
Purchase #7	$171.42	11.357%	$190.8882	$190.89	$190.90	$190.90
7 purchase totals =	$824.31		$894.9473	$894.95	$894.95	$894.90