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	$125.86	3.545%	$130.3217	$130.32	$130.30	$130.30
Purchase #2	$95.70	10.335%	$105.5906	$105.59	$105.60	$105.60
Purchase #3	$163.25	9.802%	$179.2518	$179.25	$179.25	$179.30
Purchase #4	$31.93	6.206%	$33.9116	$33.91	$33.90	$33.90
Purchase #5	$41.71	6.244%	$44.3144	$44.31	$44.30	$44.30
Purchase #6	$134.38	12.786%	$151.5618	$151.56	$151.55	$151.60
Purchase #7	$138.29	9.638%	$151.6184	$151.62	$151.60	$151.60
7 purchase totals =	$731.12		$796.5703	$796.56	$796.50	$796.60