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	$176.46	5.109%	$185.4753	$185.48	$185.50	$185.50
Purchase #2	$50.37	6.466%	$53.6269	$53.63	$53.65	$53.60
Purchase #3	$152.70	12.429%	$171.6791	$171.68	$171.70	$171.70
Purchase #4	$157.44	5.874%	$166.688	$166.69	$166.70	$166.70
Purchase #5	$43.25	11.674%	$48.299	$48.30	$48.30	$48.30
Purchase #6	$160.60	10.557%	$177.5545	$177.55	$177.55	$177.60
Purchase #7	$166.40	3.681%	$172.5252	$172.53	$172.55	$172.50
7 purchase totals =	$907.22		$975.8480	$975.86	$975.95	$975.90