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	$59.82	8.805%	$65.0872	$65.09	$65.10	$65.10
Purchase #2	$83.43	7.504%	$89.6906	$89.69	$89.70	$89.70
Purchase #3	$163.74	10.470%	$180.8836	$180.88	$180.90	$180.90
Purchase #4	$48.76	6.188%	$51.7773	$51.78	$51.80	$51.80
Purchase #5	$211.77	5.269%	$222.9282	$222.93	$222.95	$222.90
Purchase #6	$38.78	8.388%	$42.0329	$42.03	$42.05	$42.00
Purchase #7	$17.99	12.811%	$20.2947	$20.29	$20.30	$20.30
7 purchase totals =	$624.29		$672.6945	$672.69	$672.80	$672.70