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	$206.61	10.687%	$228.6904	$228.69	$228.70	$228.70
Purchase #2	$105.40	5.791%	$111.5037	$111.50	$111.50	$111.50
Purchase #3	$39.94	12.539%	$44.9481	$44.95	$44.95	$44.90
Purchase #4	$142.31	11.447%	$158.6002	$158.60	$158.60	$158.60
Purchase #5	$113.35	6.683%	$120.9252	$120.93	$120.95	$120.90
Purchase #6	$68.39	5.316%	$72.0256	$72.03	$72.05	$72.00
Purchase #7	$43.79	5.792%	$46.3263	$46.33	$46.35	$46.30
7 purchase totals =	$719.79		$783.0195	$783.03	$783.10	$782.90