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	$31.28	10.523%	$34.5716	$34.57	$34.55	$34.60
Purchase #2	$165.32	3.632%	$171.3244	$171.32	$171.30	$171.30
Purchase #3	$188.89	13.538%	$214.4619	$214.46	$214.45	$214.50
Purchase #4	$113.91	8.453%	$123.5388	$123.54	$123.55	$123.50
Purchase #5	$176.71	11.525%	$197.0758	$197.08	$197.10	$197.10
Purchase #6	$85.89	5.763%	$90.8398	$90.84	$90.85	$90.80
Purchase #7	$59.85	9.636%	$65.6171	$65.62	$65.60	$65.60
7 purchase totals =	$821.85		$897.4294	$897.43	$897.40	$897.40