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	$158.94	10.349%	$175.3887	$175.39	$175.40	$175.40
Purchase #2	$109.43	8.693%	$118.9427	$118.94	$118.95	$118.90
Purchase #3	$197.96	8.630%	$215.0439	$215.04	$215.05	$215.00
Purchase #4	$88.62	13.647%	$100.714	$100.71	$100.70	$100.70
Purchase #5	$176.81	11.176%	$196.5703	$196.57	$196.55	$196.60
Purchase #6	$59.91	5.501%	$63.2056	$63.21	$63.20	$63.20
Purchase #7	$145.75	4.116%	$151.7491	$151.75	$151.75	$151.70
7 purchase totals =	$937.42		$1,021.6143	$1,021.61	$1,021.60	$1,021.50