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	$110.57	11.312%	$123.0777	$123.08	$123.10	$123.10
Purchase #2	$55.46	11.832%	$62.022	$62.02	$62.00	$62.00
Purchase #3	$13.34	10.202%	$14.7009	$14.70	$14.70	$14.70
Purchase #4	$205.39	4.710%	$215.0639	$215.06	$215.05	$215.10
Purchase #5	$246.76	9.714%	$270.7303	$270.73	$270.75	$270.70
Purchase #6	$112.63	13.616%	$127.9657	$127.97	$127.95	$128.00
Purchase #7	$27.81	13.645%	$31.6047	$31.60	$31.60	$31.60
7 purchase totals =	$771.96		$845.1652	$845.16	$845.15	$845.20