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	$208.27	9.137%	$227.2996	$227.30	$227.30	$227.30
Purchase #2	$136.97	11.269%	$152.4051	$152.41	$152.40	$152.40
Purchase #3	$154.29	7.234%	$165.4513	$165.45	$165.45	$165.50
Purchase #4	$196.34	12.454%	$220.7922	$220.79	$220.80	$220.80
Purchase #5	$87.79	10.166%	$96.7147	$96.71	$96.70	$96.70
Purchase #6	$52.38	4.720%	$54.8523	$54.85	$54.85	$54.90
Purchase #7	$167.78	3.177%	$173.1104	$173.11	$173.10	$173.10
7 purchase totals =	$1,003.82		$1,090.6256	$1,090.62	$1,090.60	$1,090.70