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	$182.87	9.135%	$199.5752	$199.58	$199.60	$199.60
Purchase #2	$152.37	8.469%	$165.2742	$165.27	$165.25	$165.30
Purchase #3	$244.25	10.752%	$270.5118	$270.51	$270.50	$270.50
Purchase #4	$189.83	13.627%	$215.6981	$215.70	$215.70	$215.70
Purchase #5	$72.36	8.427%	$78.4578	$78.46	$78.45	$78.50
Purchase #6	$60.45	3.651%	$62.657	$62.66	$62.65	$62.70
Purchase #7	$95.41	5.870%	$101.0106	$101.01	$101.00	$101.00
7 purchase totals =	$997.54		$1,093.1847	$1,093.19	$1,093.15	$1,093.30