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	$162.36	13.544%	$184.35	$184.35	$184.35	$184.40
Purchase #2	$154.27	6.740%	$164.6678	$164.67	$164.65	$164.70
Purchase #3	$47.47	12.750%	$53.5224	$53.52	$53.50	$53.50
Purchase #4	$100.36	13.663%	$114.0722	$114.07	$114.05	$114.10
Purchase #5	$190.46	10.197%	$209.8812	$209.88	$209.90	$209.90
Purchase #6	$230.60	10.619%	$255.0874	$255.09	$255.10	$255.10
Purchase #7	$141.35	12.145%	$158.517	$158.52	$158.50	$158.50
7 purchase totals =	$1,026.87		$1,140.0980	$1,140.10	$1,140.05	$1,140.20