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	$241.75	8.326%	$261.8781	$261.88	$261.90	$261.90
Purchase #2	$85.86	3.452%	$88.8239	$88.82	$88.80	$88.80
Purchase #3	$101.92	13.652%	$115.8341	$115.83	$115.85	$115.80
Purchase #4	$247.78	8.800%	$269.5846	$269.58	$269.60	$269.60
Purchase #5	$142.38	9.610%	$156.0627	$156.06	$156.05	$156.10
Purchase #6	$104.50	11.852%	$116.8853	$116.89	$116.90	$116.90
Purchase #7	$139.82	3.510%	$144.7277	$144.73	$144.75	$144.70
7 purchase totals =	$1,064.01		$1,153.7964	$1,153.79	$1,153.85	$1,153.80