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	$227.41	6.299%	$241.7346	$241.73	$241.75	$241.70
Purchase #2	$56.67	9.171%	$61.8672	$61.87	$61.85	$61.90
Purchase #3	$60.33	7.229%	$64.6913	$64.69	$64.70	$64.70
Purchase #4	$149.65	4.528%	$156.4262	$156.43	$156.45	$156.40
Purchase #5	$126.54	3.480%	$130.9436	$130.94	$130.95	$130.90
Purchase #6	$100.28	4.726%	$105.0192	$105.02	$105.00	$105.00
Purchase #7	$187.34	9.380%	$204.9125	$204.91	$204.90	$204.90
7 purchase totals =	$908.22		$965.5946	$965.59	$965.60	$965.50