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	$182.95	4.835%	$191.7956	$191.80	$191.80	$191.80
Purchase #2	$167.75	13.587%	$190.5422	$190.54	$190.55	$190.50
Purchase #3	$207.43	3.364%	$214.4079	$214.41	$214.40	$214.40
Purchase #4	$103.75	3.870%	$107.7651	$107.77	$107.75	$107.80
Purchase #5	$114.70	12.318%	$128.8287	$128.83	$128.85	$128.80
Purchase #6	$105.86	6.288%	$112.5165	$112.52	$112.50	$112.50
Purchase #7	$245.31	13.364%	$278.0932	$278.09	$278.10	$278.10
7 purchase totals =	$1,127.75		$1,223.9492	$1,223.96	$1,223.95	$1,223.90