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	$118.89	6.107%	$126.1506	$126.15	$126.15	$126.20
Purchase #2	$199.38	4.356%	$208.065	$208.07	$208.05	$208.10
Purchase #3	$33.48	9.124%	$36.5347	$36.53	$36.55	$36.50
Purchase #4	$75.89	8.847%	$82.604	$82.60	$82.60	$82.60
Purchase #5	$230.44	4.718%	$241.3122	$241.31	$241.30	$241.30
Purchase #6	$152.61	6.670%	$162.7891	$162.79	$162.80	$162.80
Purchase #7	$247.73	12.733%	$279.2735	$279.27	$279.25	$279.30
7 purchase totals =	$1,058.42		$1,136.7291	$1,136.72	$1,136.70	$1,136.80