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	$146.52	5.305%	$154.2929	$154.29	$154.30	$154.30
Purchase #2	$92.69	3.463%	$95.8999	$95.90	$95.90	$95.90
Purchase #3	$17.78	6.330%	$18.9055	$18.91	$18.90	$18.90
Purchase #4	$163.71	9.826%	$179.7961	$179.80	$179.80	$179.80
Purchase #5	$116.31	12.838%	$131.2419	$131.24	$131.25	$131.20
Purchase #6	$115.72	10.709%	$128.1125	$128.11	$128.10	$128.10
Purchase #7	$46.87	7.791%	$50.5216	$50.52	$50.50	$50.50
7 purchase totals =	$699.60		$758.7704	$758.77	$758.75	$758.70