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	$60.25	12.575%	$67.8264	$67.83	$67.85	$67.80
Purchase #2	$91.81	9.586%	$100.6109	$100.61	$100.60	$100.60
Purchase #3	$192.85	3.179%	$198.9807	$198.98	$199.00	$199.00
Purchase #4	$221.68	12.403%	$249.175	$249.18	$249.20	$249.20
Purchase #5	$178.73	8.720%	$194.3153	$194.32	$194.30	$194.30
Purchase #6	$68.80	5.717%	$72.7333	$72.73	$72.75	$72.70
Purchase #7	$38.50	11.864%	$43.0676	$43.07	$43.05	$43.10
7 purchase totals =	$852.62		$926.7092	$926.72	$926.75	$926.70