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	$80.86	10.243%	$89.1425	$89.14	$89.15	$89.10
Purchase #2	$38.30	6.799%	$40.904	$40.90	$40.90	$40.90
Purchase #3	$115.61	5.171%	$121.5882	$121.59	$121.60	$121.60
Purchase #4	$180.86	11.269%	$201.2411	$201.24	$201.25	$201.20
Purchase #5	$62.51	5.711%	$66.0799	$66.08	$66.10	$66.10
Purchase #6	$198.45	5.653%	$209.6684	$209.67	$209.65	$209.70
Purchase #7	$32.89	4.756%	$34.4542	$34.45	$34.45	$34.50
7 purchase totals =	$709.48		$763.0783	$763.07	$763.10	$763.10