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	$38.86	10.683%	$43.0114	$43.01	$43.00	$43.00
Purchase #2	$158.52	4.449%	$165.5726	$165.57	$165.55	$165.60
Purchase #3	$55.98	6.827%	$59.8018	$59.80	$59.80	$59.80
Purchase #4	$161.78	3.729%	$167.8128	$167.81	$167.80	$167.80
Purchase #5	$77.40	11.352%	$86.1864	$86.19	$86.20	$86.20
Purchase #6	$36.25	10.598%	$40.0918	$40.09	$40.10	$40.10
Purchase #7	$167.28	9.186%	$182.6463	$182.65	$182.65	$182.60
7 purchase totals =	$696.07		$745.1231	$745.12	$745.10	$745.10