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	$79.42	7.431%	$85.3217	$85.32	$85.30	$85.30
Purchase #2	$121.74	7.700%	$131.114	$131.11	$131.10	$131.10
Purchase #3	$43.64	6.294%	$46.3867	$46.39	$46.40	$46.40
Purchase #4	$51.25	5.693%	$54.1677	$54.17	$54.15	$54.20
Purchase #5	$247.57	9.509%	$271.1114	$271.11	$271.10	$271.10
Purchase #6	$112.32	5.612%	$118.6234	$118.62	$118.60	$118.60
Purchase #7	$43.79	9.289%	$47.8577	$47.86	$47.85	$47.90
7 purchase totals =	$699.73		$754.5826	$754.58	$754.50	$754.60