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	$123.79	13.678%	$140.722	$140.72	$140.70	$140.70
Purchase #2	$55.58	11.601%	$62.0278	$62.03	$62.05	$62.00
Purchase #3	$65.57	10.400%	$72.3893	$72.39	$72.40	$72.40
Purchase #4	$148.72	9.759%	$163.2336	$163.23	$163.25	$163.20
Purchase #5	$85.31	8.342%	$92.4266	$92.43	$92.45	$92.40
Purchase #6	$111.82	5.525%	$117.9981	$118.00	$118.00	$118.00
Purchase #7	$90.67	10.607%	$100.2874	$100.29	$100.30	$100.30
7 purchase totals =	$681.46		$749.0848	$749.09	$749.15	$749.00