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	$144.33	12.192%	$161.9267	$161.93	$161.95	$161.90
Purchase #2	$152.92	3.363%	$158.0627	$158.06	$158.05	$158.10
Purchase #3	$234.88	4.233%	$244.8225	$244.82	$244.80	$244.80
Purchase #4	$231.89	3.682%	$240.4282	$240.43	$240.45	$240.40
Purchase #5	$42.40	10.437%	$46.8253	$46.83	$46.85	$46.80
Purchase #6	$211.69	7.487%	$227.5392	$227.54	$227.55	$227.50
Purchase #7	$240.70	10.443%	$265.8363	$265.84	$265.85	$265.80
7 purchase totals =	$1,258.81		$1,345.4409	$1,345.45	$1,345.50	$1,345.30