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	$166.88	5.398%	$175.8882	$175.89	$175.90	$175.90
Purchase #2	$144.39	8.604%	$156.8133	$156.81	$156.80	$156.80
Purchase #3	$137.29	5.854%	$145.327	$145.33	$145.35	$145.30
Purchase #4	$168.73	11.423%	$188.004	$188.00	$188.00	$188.00
Purchase #5	$169.41	3.256%	$174.926	$174.93	$174.95	$174.90
Purchase #6	$16.93	9.794%	$18.5881	$18.59	$18.60	$18.60
Purchase #7	$96.60	9.242%	$105.5278	$105.53	$105.55	$105.50
7 purchase totals =	$900.23		$965.0744	$965.08	$965.15	$965.00