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	$38.83	12.152%	$43.5486	$43.55	$43.55	$43.50
Purchase #2	$123.58	13.832%	$140.6736	$140.67	$140.65	$140.70
Purchase #3	$90.88	7.423%	$97.626	$97.63	$97.65	$97.60
Purchase #4	$184.27	8.676%	$200.2573	$200.26	$200.25	$200.30
Purchase #5	$188.91	6.188%	$200.5998	$200.60	$200.60	$200.60
Purchase #6	$67.84	11.133%	$75.3926	$75.39	$75.40	$75.40
Purchase #7	$154.25	11.133%	$171.4227	$171.42	$171.40	$171.40
7 purchase totals =	$848.56		$929.5206	$929.52	$929.50	$929.50