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	$95.58	10.468%	$105.5853	$105.59	$105.60	$105.60
Purchase #2	$219.48	5.215%	$230.9259	$230.93	$230.95	$230.90
Purchase #3	$124.38	10.651%	$137.6277	$137.63	$137.65	$137.60
Purchase #4	$196.87	5.362%	$207.4262	$207.43	$207.45	$207.40
Purchase #5	$124.69	9.177%	$136.1328	$136.13	$136.15	$136.10
Purchase #6	$108.91	13.256%	$123.3471	$123.35	$123.35	$123.30
Purchase #7	$67.42	9.558%	$73.864	$73.86	$73.85	$73.90
7 purchase totals =	$937.33		$1,014.9090	$1,014.92	$1,015.00	$1,014.80