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	$34.41	11.106%	$38.2316	$38.23	$38.25	$38.20
Purchase #2	$248.62	8.296%	$269.2455	$269.25	$269.25	$269.20
Purchase #3	$191.54	6.788%	$204.5417	$204.54	$204.55	$204.50
Purchase #4	$104.55	4.147%	$108.8857	$108.89	$108.90	$108.90
Purchase #5	$131.80	12.389%	$148.1287	$148.13	$148.15	$148.10
Purchase #6	$29.65	5.132%	$31.1716	$31.17	$31.15	$31.20
Purchase #7	$150.92	10.246%	$166.3833	$166.38	$166.40	$166.40
7 purchase totals =	$891.49		$966.5881	$966.59	$966.65	$966.50