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	$55.80	10.381%	$61.5926	$61.59	$61.60	$61.60
Purchase #2	$158.96	4.205%	$165.6443	$165.64	$165.65	$165.60
Purchase #3	$233.65	12.174%	$262.0946	$262.09	$262.10	$262.10
Purchase #4	$235.40	6.579%	$250.887	$250.89	$250.90	$250.90
Purchase #5	$104.71	9.725%	$114.893	$114.89	$114.90	$114.90
Purchase #6	$130.61	9.165%	$142.5804	$142.58	$142.60	$142.60
Purchase #7	$90.82	3.191%	$93.7181	$93.72	$93.70	$93.70
7 purchase totals =	$1,009.95		$1,091.4100	$1,091.40	$1,091.45	$1,091.40