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	$49.67	3.567%	$51.4417	$51.44	$51.45	$51.40
Purchase #2	$99.37	12.398%	$111.6899	$111.69	$111.70	$111.70
Purchase #3	$17.74	11.718%	$19.8188	$19.82	$19.80	$19.80
Purchase #4	$62.71	3.784%	$65.0829	$65.08	$65.10	$65.10
Purchase #5	$149.38	12.527%	$168.0928	$168.09	$168.10	$168.10
Purchase #6	$171.46	13.506%	$194.6174	$194.62	$194.60	$194.60
Purchase #7	$147.44	5.399%	$155.4003	$155.40	$155.40	$155.40
7 purchase totals =	$697.77		$766.1438	$766.14	$766.15	$766.10