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	$143.91	10.331%	$158.7773	$158.78	$158.80	$158.80
Purchase #2	$99.66	10.492%	$110.1163	$110.12	$110.10	$110.10
Purchase #3	$148.54	6.873%	$158.7492	$158.75	$158.75	$158.70
Purchase #4	$24.29	4.233%	$25.3182	$25.32	$25.30	$25.30
Purchase #5	$65.96	9.743%	$72.3865	$72.39	$72.40	$72.40
Purchase #6	$80.80	8.345%	$87.5428	$87.54	$87.55	$87.50
Purchase #7	$117.90	11.622%	$131.6023	$131.60	$131.60	$131.60
7 purchase totals =	$681.06		$744.4926	$744.50	$744.50	$744.40