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	$118.90	8.260%	$128.7211	$128.72	$128.70	$128.70
Purchase #2	$116.97	6.592%	$124.6807	$124.68	$124.70	$124.70
Purchase #3	$118.64	4.358%	$123.8103	$123.81	$123.80	$123.80
Purchase #4	$223.56	3.167%	$230.6401	$230.64	$230.65	$230.60
Purchase #5	$69.63	4.585%	$72.8225	$72.82	$72.80	$72.80
Purchase #6	$156.53	10.555%	$173.0517	$173.05	$173.05	$173.10
Purchase #7	$241.36	9.739%	$264.8661	$264.87	$264.85	$264.90
7 purchase totals =	$1,045.59		$1,118.5925	$1,118.59	$1,118.55	$1,118.60