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	$100.75	11.301%	$112.1358	$112.14	$112.15	$112.10
Purchase #2	$232.59	7.339%	$249.6598	$249.66	$249.65	$249.70
Purchase #3	$163.71	12.221%	$183.717	$183.72	$183.70	$183.70
Purchase #4	$176.35	4.578%	$184.4233	$184.42	$184.40	$184.40
Purchase #5	$142.59	8.155%	$154.2182	$154.22	$154.20	$154.20
Purchase #6	$183.87	4.156%	$191.5116	$191.51	$191.50	$191.50
Purchase #7	$100.77	3.770%	$104.569	$104.57	$104.55	$104.60
7 purchase totals =	$1,100.63		$1,180.2347	$1,180.24	$1,180.15	$1,180.20