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	$244.36	8.779%	$265.8124	$265.81	$265.80	$265.80
Purchase #2	$172.35	8.819%	$187.5495	$187.55	$187.55	$187.50
Purchase #3	$90.89	5.864%	$96.2198	$96.22	$96.20	$96.20
Purchase #4	$83.45	6.221%	$88.6414	$88.64	$88.65	$88.60
Purchase #5	$152.45	9.396%	$166.7742	$166.77	$166.75	$166.80
Purchase #6	$12.47	8.156%	$13.4871	$13.49	$13.50	$13.50
Purchase #7	$43.53	3.614%	$45.1032	$45.10	$45.10	$45.10
7 purchase totals =	$799.50		$863.5876	$863.58	$863.55	$863.50