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	$226.64	9.809%	$248.8711	$248.87	$248.85	$248.90
Purchase #2	$62.29	3.859%	$64.6938	$64.69	$64.70	$64.70
Purchase #3	$121.91	4.667%	$127.5995	$127.60	$127.60	$127.60
Purchase #4	$166.61	12.269%	$187.0514	$187.05	$187.05	$187.10
Purchase #5	$55.78	6.790%	$59.5675	$59.57	$59.55	$59.60
Purchase #6	$58.66	8.800%	$63.8221	$63.82	$63.80	$63.80
Purchase #7	$241.65	7.275%	$259.23	$259.23	$259.25	$259.20
7 purchase totals =	$933.54		$1,010.8354	$1,010.83	$1,010.80	$1,010.90