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	$222.78	5.615%	$235.2891	$235.29	$235.30	$235.30
Purchase #2	$54.28	6.577%	$57.85	$57.85	$57.85	$57.90
Purchase #3	$25.83	5.680%	$27.2971	$27.30	$27.30	$27.30
Purchase #4	$73.69	6.584%	$78.5417	$78.54	$78.55	$78.50
Purchase #5	$175.69	7.184%	$188.3116	$188.31	$188.30	$188.30
Purchase #6	$43.32	7.535%	$46.5842	$46.58	$46.60	$46.60
Purchase #7	$237.55	10.421%	$262.3051	$262.31	$262.30	$262.30
7 purchase totals =	$833.14		$896.1788	$896.18	$896.20	$896.20