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	$178.85	6.490%	$190.4574	$190.46	$190.45	$190.50
Purchase #2	$202.81	4.203%	$211.3341	$211.33	$211.35	$211.30
Purchase #3	$142.56	8.156%	$154.1872	$154.19	$154.20	$154.20
Purchase #4	$117.26	10.870%	$130.0062	$130.01	$130.00	$130.00
Purchase #5	$89.92	9.655%	$98.6018	$98.60	$98.60	$98.60
Purchase #6	$178.32	11.804%	$199.3689	$199.37	$199.35	$199.40
Purchase #7	$86.39	3.626%	$89.5225	$89.52	$89.50	$89.50
7 purchase totals =	$996.11		$1,073.4781	$1,073.48	$1,073.45	$1,073.50