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	$240.85	4.197%	$250.9585	$250.96	$250.95	$251.00
Purchase #2	$242.88	13.321%	$275.234	$275.23	$275.25	$275.20
Purchase #3	$116.65	3.135%	$120.307	$120.31	$120.30	$120.30
Purchase #4	$118.68	8.312%	$128.5447	$128.54	$128.55	$128.50
Purchase #5	$102.38	3.233%	$105.6899	$105.69	$105.70	$105.70
Purchase #6	$39.63	3.299%	$40.9374	$40.94	$40.95	$40.90
Purchase #7	$150.96	8.581%	$163.9139	$163.91	$163.90	$163.90
7 purchase totals =	$1,012.03		$1,085.5854	$1,085.58	$1,085.60	$1,085.50