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	$136.65	12.637%	$153.9185	$153.92	$153.90	$153.90
Purchase #2	$101.68	8.861%	$110.6899	$110.69	$110.70	$110.70
Purchase #3	$39.93	7.852%	$43.0653	$43.07	$43.05	$43.10
Purchase #4	$237.90	10.688%	$263.3268	$263.33	$263.35	$263.30
Purchase #5	$98.62	13.165%	$111.6033	$111.60	$111.60	$111.60
Purchase #6	$169.82	12.427%	$190.9235	$190.92	$190.90	$190.90
Purchase #7	$213.86	8.401%	$231.8264	$231.83	$231.85	$231.80
7 purchase totals =	$998.46		$1,105.3537	$1,105.36	$1,105.35	$1,105.30