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	$127.75	9.107%	$139.3842	$139.38	$139.40	$139.40
Purchase #2	$167.44	11.275%	$186.3189	$186.32	$186.30	$186.30
Purchase #3	$156.79	5.562%	$165.5107	$165.51	$165.50	$165.50
Purchase #4	$193.37	9.726%	$212.1772	$212.18	$212.20	$212.20
Purchase #5	$70.78	11.545%	$78.9516	$78.95	$78.95	$79.00
Purchase #6	$146.80	6.767%	$156.734	$156.73	$156.75	$156.70
Purchase #7	$117.76	12.832%	$132.871	$132.87	$132.85	$132.90
7 purchase totals =	$980.69		$1,071.9476	$1,071.94	$1,071.95	$1,072.00