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	$169.61	6.538%	$180.6991	$180.70	$180.70	$180.70
Purchase #2	$186.49	4.292%	$194.4942	$194.49	$194.50	$194.50
Purchase #3	$131.68	13.355%	$149.2659	$149.27	$149.25	$149.30
Purchase #4	$158.75	13.391%	$180.0082	$180.01	$180.00	$180.00
Purchase #5	$48.95	5.838%	$51.8077	$51.81	$51.80	$51.80
Purchase #6	$181.89	7.841%	$196.152	$196.15	$196.15	$196.20
Purchase #7	$54.77	8.162%	$59.2403	$59.24	$59.25	$59.20
7 purchase totals =	$932.14		$1,011.6674	$1,011.67	$1,011.65	$1,011.70