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	$24.34	5.142%	$25.5916	$25.59	$25.60	$25.60
Purchase #2	$45.55	11.680%	$50.8702	$50.87	$50.85	$50.90
Purchase #3	$117.40	12.357%	$131.9071	$131.91	$131.90	$131.90
Purchase #4	$67.55	6.528%	$71.9597	$71.96	$71.95	$72.00
Purchase #5	$203.63	6.451%	$216.7662	$216.77	$216.75	$216.80
Purchase #6	$114.26	9.525%	$125.1433	$125.14	$125.15	$125.10
Purchase #7	$52.93	3.238%	$54.6439	$54.64	$54.65	$54.60
7 purchase totals =	$625.66		$676.8820	$676.88	$676.85	$676.90