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	$208.41	13.466%	$236.4745	$236.47	$236.45	$236.50
Purchase #2	$71.29	7.615%	$76.7187	$76.72	$76.70	$76.70
Purchase #3	$228.47	11.686%	$255.169	$255.17	$255.15	$255.20
Purchase #4	$160.91	6.500%	$171.3692	$171.37	$171.35	$171.40
Purchase #5	$18.96	13.478%	$21.5154	$21.52	$21.50	$21.50
Purchase #6	$184.47	6.549%	$196.5509	$196.55	$196.55	$196.60
Purchase #7	$112.83	11.752%	$126.0898	$126.09	$126.10	$126.10
7 purchase totals =	$985.34		$1,083.8875	$1,083.89	$1,083.80	$1,084.00