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	$161.92	12.189%	$181.6564	$181.66	$181.65	$181.70
Purchase #2	$231.62	8.370%	$251.0066	$251.01	$251.00	$251.00
Purchase #3	$185.73	5.838%	$196.5729	$196.57	$196.55	$196.60
Purchase #4	$104.73	6.627%	$111.6705	$111.67	$111.65	$111.70
Purchase #5	$113.84	9.372%	$124.5091	$124.51	$124.50	$124.50
Purchase #6	$132.35	12.866%	$149.3782	$149.38	$149.40	$149.40
Purchase #7	$83.40	7.179%	$89.3873	$89.39	$89.40	$89.40
7 purchase totals =	$1,013.59		$1,104.1810	$1,104.19	$1,104.15	$1,104.30