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	$41.26	4.587%	$43.1526	$43.15	$43.15	$43.20
Purchase #2	$79.89	13.298%	$90.5138	$90.51	$90.50	$90.50
Purchase #3	$103.96	7.359%	$111.6104	$111.61	$111.60	$111.60
Purchase #4	$221.26	13.484%	$251.0947	$251.09	$251.10	$251.10
Purchase #5	$143.37	7.725%	$154.4453	$154.45	$154.45	$154.40
Purchase #6	$232.68	7.108%	$249.2189	$249.22	$249.20	$249.20
Purchase #7	$197.89	4.483%	$206.7614	$206.76	$206.75	$206.80
7 purchase totals =	$1,020.31		$1,106.7971	$1,106.79	$1,106.75	$1,106.80