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	$158.60	4.390%	$165.5625	$165.56	$165.55	$165.60
Purchase #2	$152.54	10.469%	$168.5094	$168.51	$168.50	$168.50
Purchase #3	$210.89	11.456%	$235.0496	$235.05	$235.05	$235.00
Purchase #4	$184.39	7.643%	$198.4829	$198.48	$198.50	$198.50
Purchase #5	$38.78	5.627%	$40.9622	$40.96	$40.95	$41.00
Purchase #6	$244.65	5.501%	$258.1082	$258.11	$258.10	$258.10
Purchase #7	$153.75	11.682%	$171.7111	$171.71	$171.70	$171.70
7 purchase totals =	$1,143.60		$1,238.3859	$1,238.38	$1,238.35	$1,238.40