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	$211.87	3.411%	$219.0969	$219.10	$219.10	$219.10
Purchase #2	$183.80	9.136%	$200.592	$200.59	$200.60	$200.60
Purchase #3	$74.31	6.174%	$78.8979	$78.90	$78.90	$78.90
Purchase #4	$135.45	4.727%	$141.8527	$141.85	$141.85	$141.90
Purchase #5	$98.47	6.824%	$105.1896	$105.19	$105.20	$105.20
Purchase #6	$52.91	12.634%	$59.5946	$59.59	$59.60	$59.60
Purchase #7	$247.39	9.115%	$269.9396	$269.94	$269.95	$269.90
7 purchase totals =	$1,004.20		$1,075.1633	$1,075.16	$1,075.20	$1,075.20