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	$100.32	11.237%	$111.593	$111.59	$111.60	$111.60
Purchase #2	$70.60	11.412%	$78.6569	$78.66	$78.65	$78.70
Purchase #3	$86.50	7.365%	$92.8707	$92.87	$92.85	$92.90
Purchase #4	$135.29	9.308%	$147.8828	$147.88	$147.90	$147.90
Purchase #5	$101.50	9.780%	$111.4267	$111.43	$111.45	$111.40
Purchase #6	$89.83	4.483%	$93.8571	$93.86	$93.85	$93.90
Purchase #7	$97.50	3.238%	$100.6571	$100.66	$100.65	$100.70
7 purchase totals =	$681.54		$736.9443	$736.95	$736.95	$737.10