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	$56.67	8.860%	$61.691	$61.69	$61.70	$61.70
Purchase #2	$162.58	10.541%	$179.7176	$179.72	$179.70	$179.70
Purchase #3	$69.67	12.316%	$78.2506	$78.25	$78.25	$78.30
Purchase #4	$41.75	3.648%	$43.273	$43.27	$43.25	$43.30
Purchase #5	$131.75	3.404%	$136.2348	$136.23	$136.25	$136.20
Purchase #6	$49.55	5.174%	$52.1137	$52.11	$52.10	$52.10
Purchase #7	$230.39	10.506%	$254.5948	$254.59	$254.60	$254.60
7 purchase totals =	$742.36		$805.8755	$805.86	$805.85	$805.90