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	$242.84	8.492%	$263.462	$263.46	$263.45	$263.50
Purchase #2	$222.39	7.770%	$239.6697	$239.67	$239.65	$239.70
Purchase #3	$82.92	7.659%	$89.2708	$89.27	$89.25	$89.30
Purchase #4	$233.93	4.541%	$244.5528	$244.55	$244.55	$244.60
Purchase #5	$18.84	3.230%	$19.4485	$19.45	$19.45	$19.40
Purchase #6	$108.70	3.758%	$112.7849	$112.78	$112.80	$112.80
Purchase #7	$84.49	13.799%	$96.1488	$96.15	$96.15	$96.10
7 purchase totals =	$994.11		$1,065.3375	$1,065.33	$1,065.30	$1,065.40