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	$217.47	5.681%	$229.8245	$229.82	$229.80	$229.80
Purchase #2	$241.98	7.401%	$259.8889	$259.89	$259.90	$259.90
Purchase #3	$77.40	6.536%	$82.4589	$82.46	$82.45	$82.50
Purchase #4	$47.72	12.683%	$53.7723	$53.77	$53.75	$53.80
Purchase #5	$50.36	12.742%	$56.7769	$56.78	$56.80	$56.80
Purchase #6	$237.69	13.508%	$269.7972	$269.80	$269.80	$269.80
Purchase #7	$56.38	6.521%	$60.0565	$60.06	$60.05	$60.10
7 purchase totals =	$929.00		$1,012.5752	$1,012.58	$1,012.55	$1,012.70