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	$180.99	8.775%	$196.8719	$196.87	$196.85	$196.90
Purchase #2	$150.93	11.806%	$168.7488	$168.75	$168.75	$168.70
Purchase #3	$78.41	13.856%	$89.2745	$89.27	$89.25	$89.30
Purchase #4	$71.62	7.205%	$76.7802	$76.78	$76.80	$76.80
Purchase #5	$130.58	9.290%	$142.7109	$142.71	$142.70	$142.70
Purchase #6	$71.29	6.727%	$76.0857	$76.09	$76.10	$76.10
Purchase #7	$109.79	10.337%	$121.139	$121.14	$121.15	$121.10
7 purchase totals =	$793.61		$871.6110	$871.61	$871.60	$871.60