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	$82.38	9.498%	$90.2045	$90.20	$90.20	$90.20
Purchase #2	$212.89	6.839%	$227.4495	$227.45	$227.45	$227.40
Purchase #3	$148.36	4.400%	$154.8878	$154.89	$154.90	$154.90
Purchase #4	$204.99	4.641%	$214.5036	$214.50	$214.50	$214.50
Purchase #5	$85.78	8.270%	$92.874	$92.87	$92.85	$92.90
Purchase #6	$182.96	12.222%	$205.3214	$205.32	$205.30	$205.30
Purchase #7	$30.49	10.762%	$33.7713	$33.77	$33.75	$33.80
7 purchase totals =	$947.85		$1,019.0121	$1,019.00	$1,018.95	$1,019.00