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	$230.59	13.681%	$262.137	$262.14	$262.15	$262.10
Purchase #2	$118.41	8.460%	$128.4275	$128.43	$128.45	$128.40
Purchase #3	$240.81	10.280%	$265.5653	$265.57	$265.55	$265.60
Purchase #4	$123.59	10.518%	$136.5892	$136.59	$136.60	$136.60
Purchase #5	$6.75	7.602%	$7.2631	$7.26	$7.25	$7.30
Purchase #6	$69.57	4.542%	$72.7299	$72.73	$72.75	$72.70
Purchase #7	$175.76	4.188%	$183.1208	$183.12	$183.10	$183.10
7 purchase totals =	$965.48		$1,055.8328	$1,055.84	$1,055.85	$1,055.80