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	$246.88	6.597%	$263.1667	$263.17	$263.15	$263.20
Purchase #2	$41.46	11.731%	$46.3237	$46.32	$46.30	$46.30
Purchase #3	$116.70	13.319%	$132.2433	$132.24	$132.25	$132.20
Purchase #4	$219.95	4.721%	$230.3338	$230.33	$230.35	$230.30
Purchase #5	$27.45	13.168%	$31.0646	$31.06	$31.05	$31.10
Purchase #6	$237.90	7.446%	$255.614	$255.61	$255.60	$255.60
Purchase #7	$215.60	5.201%	$226.8134	$226.81	$226.80	$226.80
7 purchase totals =	$1,105.94		$1,185.5595	$1,185.54	$1,185.50	$1,185.50