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	$212.35	6.282%	$225.6898	$225.69	$225.70	$225.70
Purchase #2	$182.58	8.439%	$197.9879	$197.99	$198.00	$198.00
Purchase #3	$19.72	6.807%	$21.0623	$21.06	$21.05	$21.10
Purchase #4	$104.52	6.714%	$111.5375	$111.54	$111.55	$111.50
Purchase #5	$192.71	10.750%	$213.4263	$213.43	$213.45	$213.40
Purchase #6	$178.86	3.652%	$185.392	$185.39	$185.40	$185.40
Purchase #7	$49.46	9.394%	$54.1063	$54.11	$54.10	$54.10
7 purchase totals =	$940.20		$1,009.2021	$1,009.21	$1,009.25	$1,009.20