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	$76.96	4.704%	$80.5802	$80.58	$80.60	$80.60
Purchase #2	$11.62	6.124%	$12.3316	$12.33	$12.35	$12.30
Purchase #3	$117.88	5.618%	$124.5025	$124.50	$124.50	$124.50
Purchase #4	$104.65	3.665%	$108.4854	$108.49	$108.50	$108.50
Purchase #5	$229.28	3.292%	$236.8279	$236.83	$236.85	$236.80
Purchase #6	$174.60	12.414%	$196.2748	$196.27	$196.25	$196.30
Purchase #7	$14.90	11.339%	$16.5895	$16.59	$16.60	$16.60
7 purchase totals =	$729.89		$775.5919	$775.59	$775.65	$775.60