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	$187.36	5.307%	$197.3032	$197.30	$197.30	$197.30
Purchase #2	$65.34	10.508%	$72.2059	$72.21	$72.20	$72.20
Purchase #3	$19.45	8.380%	$21.0799	$21.08	$21.10	$21.10
Purchase #4	$181.32	9.331%	$198.239	$198.24	$198.25	$198.20
Purchase #5	$87.78	9.470%	$96.0928	$96.09	$96.10	$96.10
Purchase #6	$38.27	12.512%	$43.0583	$43.06	$43.05	$43.10
Purchase #7	$10.86	5.718%	$11.481	$11.48	$11.50	$11.50
7 purchase totals =	$590.38		$639.4601	$639.46	$639.50	$639.50