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	$241.54	3.747%	$250.5905	$250.59	$250.60	$250.60
Purchase #2	$162.82	6.603%	$173.571	$173.57	$173.55	$173.60
Purchase #3	$62.27	12.181%	$69.8551	$69.86	$69.85	$69.90
Purchase #4	$133.56	10.582%	$147.6933	$147.69	$147.70	$147.70
Purchase #5	$133.45	13.214%	$151.0841	$151.08	$151.10	$151.10
Purchase #6	$222.90	4.567%	$233.0798	$233.08	$233.10	$233.10
Purchase #7	$52.39	8.333%	$56.7557	$56.76	$56.75	$56.80
7 purchase totals =	$1,008.93		$1,082.6295	$1,082.63	$1,082.65	$1,082.80