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	$51.77	3.542%	$53.6037	$53.60	$53.60	$53.60
Purchase #2	$92.33	4.618%	$96.5938	$96.59	$96.60	$96.60
Purchase #3	$146.60	10.286%	$161.6793	$161.68	$161.70	$161.70
Purchase #4	$38.66	12.330%	$43.4268	$43.43	$43.45	$43.40
Purchase #5	$175.79	7.403%	$188.8037	$188.80	$188.80	$188.80
Purchase #6	$151.82	9.839%	$166.7576	$166.76	$166.75	$166.80
Purchase #7	$59.70	3.211%	$61.617	$61.62	$61.60	$61.60
7 purchase totals =	$716.67		$772.4819	$772.48	$772.50	$772.50