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	$235.30	11.494%	$262.3454	$262.35	$262.35	$262.30
Purchase #2	$103.70	7.793%	$111.7813	$111.78	$111.80	$111.80
Purchase #3	$96.71	6.644%	$103.1354	$103.14	$103.15	$103.10
Purchase #4	$191.99	12.865%	$216.6895	$216.69	$216.70	$216.70
Purchase #5	$102.35	10.248%	$112.8388	$112.84	$112.85	$112.80
Purchase #6	$100.40	12.483%	$112.9329	$112.93	$112.95	$112.90
Purchase #7	$78.60	13.695%	$89.3643	$89.36	$89.35	$89.40
7 purchase totals =	$909.05		$1,009.0876	$1,009.09	$1,009.15	$1,009.00