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	$43.44	6.195%	$46.1311	$46.13	$46.15	$46.10
Purchase #2	$89.80	7.663%	$96.6814	$96.68	$96.70	$96.70
Purchase #3	$15.73	5.280%	$16.5605	$16.56	$16.55	$16.60
Purchase #4	$119.41	10.236%	$131.6328	$131.63	$131.65	$131.60
Purchase #5	$238.90	10.849%	$264.8183	$264.82	$264.80	$264.80
Purchase #6	$190.89	7.712%	$205.6114	$205.61	$205.60	$205.60
Purchase #7	$11.42	9.396%	$12.493	$12.49	$12.50	$12.50
7 purchase totals =	$709.59		$773.9285	$773.92	$773.95	$773.90