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	$186.77	10.777%	$206.8982	$206.90	$206.90	$206.90
Purchase #2	$153.78	7.141%	$164.7614	$164.76	$164.75	$164.80
Purchase #3	$28.71	13.677%	$32.6367	$32.64	$32.65	$32.60
Purchase #4	$230.38	9.315%	$251.8399	$251.84	$251.85	$251.80
Purchase #5	$150.76	3.281%	$155.7064	$155.71	$155.70	$155.70
Purchase #6	$33.33	12.299%	$37.4293	$37.43	$37.45	$37.40
Purchase #7	$202.77	4.808%	$212.5192	$212.52	$212.50	$212.50
7 purchase totals =	$986.50		$1,061.7911	$1,061.80	$1,061.80	$1,061.70