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	$208.45	10.302%	$229.9245	$229.92	$229.90	$229.90
Purchase #2	$46.79	8.509%	$50.7714	$50.77	$50.75	$50.80
Purchase #3	$41.60	10.296%	$45.8831	$45.88	$45.90	$45.90
Purchase #4	$80.52	11.416%	$89.7122	$89.71	$89.70	$89.70
Purchase #5	$160.46	3.795%	$166.5495	$166.55	$166.55	$166.50
Purchase #6	$208.60	9.542%	$228.5046	$228.50	$228.50	$228.50
Purchase #7	$45.59	9.272%	$49.8171	$49.82	$49.80	$49.80
7 purchase totals =	$792.01		$861.1624	$861.15	$861.10	$861.10