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	$183.70	9.363%	$200.8998	$200.90	$200.90	$200.90
Purchase #2	$34.58	13.794%	$39.35	$39.35	$39.35	$39.40
Purchase #3	$136.92	3.247%	$141.3658	$141.37	$141.35	$141.40
Purchase #4	$221.62	13.384%	$251.2816	$251.28	$251.30	$251.30
Purchase #5	$38.86	11.597%	$43.3666	$43.37	$43.35	$43.40
Purchase #6	$229.33	4.105%	$238.744	$238.74	$238.75	$238.70
Purchase #7	$158.52	8.121%	$171.3934	$171.39	$171.40	$171.40
7 purchase totals =	$1,003.53		$1,086.4012	$1,086.40	$1,086.40	$1,086.50