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	$221.60	7.835%	$238.9624	$238.96	$238.95	$239.00
Purchase #2	$112.80	6.836%	$120.511	$120.51	$120.50	$120.50
Purchase #3	$85.95	6.317%	$91.3795	$91.38	$91.40	$91.40
Purchase #4	$17.91	12.496%	$20.148	$20.15	$20.15	$20.10
Purchase #5	$48.91	10.496%	$54.0436	$54.04	$54.05	$54.00
Purchase #6	$10.65	10.495%	$11.7677	$11.77	$11.75	$11.80
Purchase #7	$169.84	5.161%	$178.6054	$178.61	$178.60	$178.60
7 purchase totals =	$667.66		$715.4176	$715.42	$715.40	$715.40