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	$64.77	6.619%	$69.0571	$69.06	$69.05	$69.10
Purchase #2	$55.29	8.127%	$59.7834	$59.78	$59.80	$59.80
Purchase #3	$16.98	7.258%	$18.2124	$18.21	$18.20	$18.20
Purchase #4	$171.41	7.818%	$184.8108	$184.81	$184.80	$184.80
Purchase #5	$30.87	9.154%	$33.6958	$33.70	$33.70	$33.70
Purchase #6	$200.52	9.490%	$219.5493	$219.55	$219.55	$219.50
Purchase #7	$98.79	12.824%	$111.4588	$111.46	$111.45	$111.50
7 purchase totals =	$638.63		$696.5676	$696.57	$696.55	$696.60