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	$247.25	12.572%	$278.3343	$278.33	$278.35	$278.30
Purchase #2	$65.43	3.710%	$67.8575	$67.86	$67.85	$67.90
Purchase #3	$105.64	4.518%	$110.4128	$110.41	$110.40	$110.40
Purchase #4	$248.65	3.103%	$256.3656	$256.37	$256.35	$256.40
Purchase #5	$150.29	5.361%	$158.347	$158.35	$158.35	$158.30
Purchase #6	$11.55	3.129%	$11.9114	$11.91	$11.90	$11.90
Purchase #7	$165.96	5.509%	$175.1027	$175.10	$175.10	$175.10
7 purchase totals =	$994.77		$1,058.3313	$1,058.33	$1,058.30	$1,058.30