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	$17.94	7.724%	$19.3257	$19.33	$19.35	$19.30
Purchase #2	$31.64	4.752%	$33.1435	$33.14	$33.15	$33.10
Purchase #3	$69.34	12.407%	$77.943	$77.94	$77.95	$77.90
Purchase #4	$200.81	11.358%	$223.618	$223.62	$223.60	$223.60
Purchase #5	$182.92	5.214%	$192.4574	$192.46	$192.45	$192.50
Purchase #6	$91.42	8.612%	$99.2931	$99.29	$99.30	$99.30
Purchase #7	$39.30	9.128%	$42.8873	$42.89	$42.90	$42.90
7 purchase totals =	$633.37		$688.6680	$688.67	$688.70	$688.60