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	$40.77	11.527%	$45.4696	$45.47	$45.45	$45.50
Purchase #2	$177.65	7.456%	$190.8956	$190.90	$190.90	$190.90
Purchase #3	$163.57	12.129%	$183.4094	$183.41	$183.40	$183.40
Purchase #4	$205.59	3.140%	$212.0455	$212.05	$212.05	$212.00
Purchase #5	$184.42	4.757%	$193.1929	$193.19	$193.20	$193.20
Purchase #6	$159.61	12.409%	$179.416	$179.42	$179.40	$179.40
Purchase #7	$79.96	3.577%	$82.8202	$82.82	$82.80	$82.80
7 purchase totals =	$1,011.57		$1,087.2492	$1,087.26	$1,087.20	$1,087.20