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	$32.35	9.854%	$35.5378	$35.54	$35.55	$35.50
Purchase #2	$75.85	13.221%	$85.8781	$85.88	$85.90	$85.90
Purchase #3	$153.40	4.811%	$160.7801	$160.78	$160.80	$160.80
Purchase #4	$146.55	3.684%	$151.9489	$151.95	$151.95	$151.90
Purchase #5	$38.75	10.164%	$42.6886	$42.69	$42.70	$42.70
Purchase #6	$81.71	6.631%	$87.1282	$87.13	$87.15	$87.10
Purchase #7	$177.58	12.811%	$200.3298	$200.33	$200.35	$200.30
7 purchase totals =	$706.19		$764.2915	$764.30	$764.40	$764.20