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	$190.82	9.849%	$209.6139	$209.61	$209.60	$209.60
Purchase #2	$173.44	11.840%	$193.9753	$193.98	$194.00	$194.00
Purchase #3	$110.98	7.783%	$119.6176	$119.62	$119.60	$119.60
Purchase #4	$31.60	9.615%	$34.6383	$34.64	$34.65	$34.60
Purchase #5	$169.54	5.341%	$178.5951	$178.60	$178.60	$178.60
Purchase #6	$43.53	11.627%	$48.5912	$48.59	$48.60	$48.60
Purchase #7	$173.52	13.190%	$196.4073	$196.41	$196.40	$196.40
7 purchase totals =	$893.43		$981.4387	$981.45	$981.45	$981.40