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	$208.33	13.649%	$236.765	$236.77	$236.75	$236.80
Purchase #2	$103.80	13.209%	$117.5109	$117.51	$117.50	$117.50
Purchase #3	$165.84	5.181%	$174.4322	$174.43	$174.45	$174.40
Purchase #4	$78.72	4.242%	$82.0593	$82.06	$82.05	$82.10
Purchase #5	$156.68	9.758%	$171.9688	$171.97	$171.95	$172.00
Purchase #6	$183.27	13.524%	$208.0554	$208.06	$208.05	$208.10
Purchase #7	$81.60	4.550%	$85.3128	$85.31	$85.30	$85.30
7 purchase totals =	$978.24		$1,076.1044	$1,076.11	$1,076.05	$1,076.20