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	$47.85	5.798%	$50.6243	$50.62	$50.60	$50.60
Purchase #2	$17.64	12.274%	$19.8051	$19.81	$19.80	$19.80
Purchase #3	$114.81	10.739%	$127.1394	$127.14	$127.15	$127.10
Purchase #4	$55.27	11.340%	$61.5376	$61.54	$61.55	$61.50
Purchase #5	$56.80	7.466%	$61.0407	$61.04	$61.05	$61.00
Purchase #6	$190.90	4.104%	$198.7345	$198.73	$198.75	$198.70
Purchase #7	$210.42	12.327%	$236.3585	$236.36	$236.35	$236.40
7 purchase totals =	$693.69		$755.2401	$755.24	$755.25	$755.10