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	$214.38	6.419%	$228.1411	$228.14	$228.15	$228.10
Purchase #2	$97.46	9.404%	$106.6251	$106.63	$106.65	$106.60
Purchase #3	$175.29	4.742%	$183.6023	$183.60	$183.60	$183.60
Purchase #4	$176.54	12.658%	$198.8864	$198.89	$198.90	$198.90
Purchase #5	$180.77	8.784%	$196.6488	$196.65	$196.65	$196.60
Purchase #6	$113.27	4.105%	$117.9197	$117.92	$117.90	$117.90
Purchase #7	$222.75	3.732%	$231.063	$231.06	$231.05	$231.10
7 purchase totals =	$1,180.46		$1,262.8864	$1,262.89	$1,262.90	$1,262.80