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	$49.52	13.738%	$56.3231	$56.32	$56.30	$56.30
Purchase #2	$50.46	5.766%	$53.3695	$53.37	$53.35	$53.40
Purchase #3	$206.42	4.416%	$215.5355	$215.54	$215.55	$215.50
Purchase #4	$67.38	6.580%	$71.8136	$71.81	$71.80	$71.80
Purchase #5	$69.40	6.102%	$73.6348	$73.63	$73.65	$73.60
Purchase #6	$198.92	10.502%	$219.8106	$219.81	$219.80	$219.80
Purchase #7	$68.59	3.660%	$71.1004	$71.10	$71.10	$71.10
7 purchase totals =	$710.69		$761.5875	$761.58	$761.55	$761.50