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	$132.97	13.264%	$150.6071	$150.61	$150.60	$150.60
Purchase #2	$109.37	4.498%	$114.2895	$114.29	$114.30	$114.30
Purchase #3	$20.35	7.555%	$21.8874	$21.89	$21.90	$21.90
Purchase #4	$107.81	7.235%	$115.6101	$115.61	$115.60	$115.60
Purchase #5	$217.39	13.582%	$246.9159	$246.92	$246.90	$246.90
Purchase #6	$85.83	4.148%	$89.3902	$89.39	$89.40	$89.40
Purchase #7	$18.70	6.609%	$19.9359	$19.94	$19.95	$19.90
7 purchase totals =	$692.42		$758.6361	$758.65	$758.65	$758.60