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	$65.97	3.234%	$68.1035	$68.10	$68.10	$68.10
Purchase #2	$149.42	11.808%	$167.0635	$167.06	$167.05	$167.10
Purchase #3	$215.39	11.157%	$239.4211	$239.42	$239.40	$239.40
Purchase #4	$172.83	13.673%	$196.461	$196.46	$196.45	$196.50
Purchase #5	$163.91	9.608%	$179.6585	$179.66	$179.65	$179.70
Purchase #6	$72.35	8.193%	$78.2776	$78.28	$78.30	$78.30
Purchase #7	$227.56	11.429%	$253.5678	$253.57	$253.55	$253.60
7 purchase totals =	$1,067.43		$1,182.5530	$1,182.55	$1,182.50	$1,182.70