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	$13.91	4.229%	$14.4983	$14.50	$14.50	$14.50
Purchase #2	$168.32	9.280%	$183.9401	$183.94	$183.95	$183.90
Purchase #3	$18.94	3.506%	$19.604	$19.60	$19.60	$19.60
Purchase #4	$172.46	13.748%	$196.1698	$196.17	$196.15	$196.20
Purchase #5	$215.85	5.232%	$227.1433	$227.14	$227.15	$227.10
Purchase #6	$146.90	13.833%	$167.2207	$167.22	$167.20	$167.20
Purchase #7	$28.62	9.281%	$31.2762	$31.28	$31.30	$31.30
7 purchase totals =	$765.00		$839.8524	$839.85	$839.85	$839.80