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	$34.38	12.632%	$38.7229	$38.72	$38.70	$38.70
Purchase #2	$47.46	7.591%	$51.0627	$51.06	$51.05	$51.10
Purchase #3	$235.92	3.838%	$244.9746	$244.97	$244.95	$245.00
Purchase #4	$240.50	7.387%	$258.2657	$258.27	$258.25	$258.30
Purchase #5	$144.50	5.655%	$152.6715	$152.67	$152.65	$152.70
Purchase #6	$72.91	8.104%	$78.8186	$78.82	$78.80	$78.80
Purchase #7	$183.25	8.745%	$199.2752	$199.28	$199.30	$199.30
7 purchase totals =	$958.92		$1,023.7912	$1,023.79	$1,023.70	$1,023.90