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	$222.90	3.496%	$230.6926	$230.69	$230.70	$230.70
Purchase #2	$145.83	13.307%	$165.2356	$165.24	$165.25	$165.20
Purchase #3	$130.36	10.611%	$144.1925	$144.19	$144.20	$144.20
Purchase #4	$47.56	10.138%	$52.3816	$52.38	$52.40	$52.40
Purchase #5	$165.78	12.217%	$186.0333	$186.03	$186.05	$186.00
Purchase #6	$222.34	7.758%	$239.5891	$239.59	$239.60	$239.60
Purchase #7	$88.56	13.771%	$100.7556	$100.76	$100.75	$100.80
7 purchase totals =	$1,023.33		$1,118.8803	$1,118.88	$1,118.95	$1,118.90