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	$110.93	7.172%	$118.8859	$118.89	$118.90	$118.90
Purchase #2	$131.40	11.581%	$146.6174	$146.62	$146.60	$146.60
Purchase #3	$52.48	6.649%	$55.9694	$55.97	$55.95	$56.00
Purchase #4	$43.88	5.635%	$46.3526	$46.35	$46.35	$46.40
Purchase #5	$54.87	13.104%	$62.0602	$62.06	$62.05	$62.10
Purchase #6	$61.51	6.153%	$65.2947	$65.29	$65.30	$65.30
Purchase #7	$117.53	12.154%	$131.8146	$131.81	$131.80	$131.80
7 purchase totals =	$572.60		$626.9948	$626.99	$626.95	$627.10