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	$187.77	12.179%	$210.6385	$210.64	$210.65	$210.60
Purchase #2	$174.68	11.128%	$194.1184	$194.12	$194.10	$194.10
Purchase #3	$42.65	6.516%	$45.4291	$45.43	$45.45	$45.40
Purchase #4	$72.29	11.622%	$80.6915	$80.69	$80.70	$80.70
Purchase #5	$241.79	3.162%	$249.4354	$249.44	$249.45	$249.40
Purchase #6	$120.72	5.445%	$127.2932	$127.29	$127.30	$127.30
Purchase #7	$130.41	13.397%	$147.881	$147.88	$147.90	$147.90
7 purchase totals =	$970.31		$1,055.4871	$1,055.49	$1,055.55	$1,055.40