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	$97.40	6.850%	$104.0719	$104.07	$104.05	$104.10
Purchase #2	$143.82	6.357%	$152.9626	$152.96	$152.95	$153.00
Purchase #3	$50.46	6.832%	$53.9074	$53.91	$53.90	$53.90
Purchase #4	$54.65	9.225%	$59.6915	$59.69	$59.70	$59.70
Purchase #5	$139.99	3.359%	$144.6923	$144.69	$144.70	$144.70
Purchase #6	$41.82	3.344%	$43.2185	$43.22	$43.20	$43.20
Purchase #7	$118.84	8.486%	$128.9248	$128.92	$128.90	$128.90
7 purchase totals =	$646.98		$687.4690	$687.46	$687.40	$687.50