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	$72.66	8.231%	$78.6406	$78.64	$78.65	$78.60
Purchase #2	$194.51	5.347%	$204.9104	$204.91	$204.90	$204.90
Purchase #3	$39.51	12.357%	$44.3923	$44.39	$44.40	$44.40
Purchase #4	$166.66	5.475%	$175.7846	$175.78	$175.80	$175.80
Purchase #5	$142.76	7.617%	$153.634	$153.63	$153.65	$153.60
Purchase #6	$181.77	10.290%	$200.4741	$200.47	$200.45	$200.50
Purchase #7	$200.81	6.295%	$213.451	$213.45	$213.45	$213.50
7 purchase totals =	$998.68		$1,071.2870	$1,071.27	$1,071.30	$1,071.30