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	$77.32	11.327%	$86.078	$86.08	$86.10	$86.10
Purchase #2	$214.85	5.829%	$227.3736	$227.37	$227.35	$227.40
Purchase #3	$79.90	13.818%	$90.9406	$90.94	$90.95	$90.90
Purchase #4	$73.51	7.398%	$78.9483	$78.95	$78.95	$78.90
Purchase #5	$122.68	3.704%	$127.2241	$127.22	$127.20	$127.20
Purchase #6	$233.95	9.399%	$255.939	$255.94	$255.95	$255.90
Purchase #7	$163.76	12.433%	$184.1203	$184.12	$184.10	$184.10
7 purchase totals =	$965.97		$1,050.6239	$1,050.62	$1,050.60	$1,050.50