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	$49.54	7.286%	$53.1495	$53.15	$53.15	$53.10
Purchase #2	$224.83	6.524%	$239.4979	$239.50	$239.50	$239.50
Purchase #3	$165.69	6.458%	$176.3903	$176.39	$176.40	$176.40
Purchase #4	$198.40	10.242%	$218.7201	$218.72	$218.70	$218.70
Purchase #5	$225.91	3.554%	$233.9388	$233.94	$233.95	$233.90
Purchase #6	$32.51	3.129%	$33.5272	$33.53	$33.55	$33.50
Purchase #7	$43.38	13.843%	$49.3851	$49.39	$49.40	$49.40
7 purchase totals =	$940.26		$1,004.6089	$1,004.62	$1,004.65	$1,004.50