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	$105.84	3.173%	$109.1983	$109.20	$109.20	$109.20
Purchase #2	$142.94	6.757%	$152.5985	$152.60	$152.60	$152.60
Purchase #3	$29.38	13.622%	$33.3821	$33.38	$33.40	$33.40
Purchase #4	$174.91	13.833%	$199.1053	$199.11	$199.10	$199.10
Purchase #5	$131.83	10.131%	$145.1857	$145.19	$145.20	$145.20
Purchase #6	$98.52	6.840%	$105.2588	$105.26	$105.25	$105.30
Purchase #7	$9.40	7.237%	$10.0803	$10.08	$10.10	$10.10
7 purchase totals =	$692.82		$754.8090	$754.82	$754.85	$754.90