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	$123.63	4.298%	$128.9436	$128.94	$128.95	$128.90
Purchase #2	$20.86	12.828%	$23.5359	$23.54	$23.55	$23.50
Purchase #3	$142.56	9.645%	$156.3099	$156.31	$156.30	$156.30
Purchase #4	$229.65	11.291%	$255.5798	$255.58	$255.60	$255.60
Purchase #5	$61.96	3.160%	$63.9179	$63.92	$63.90	$63.90
Purchase #6	$205.39	7.658%	$221.1188	$221.12	$221.10	$221.10
Purchase #7	$194.48	12.212%	$218.2299	$218.23	$218.25	$218.20
7 purchase totals =	$978.53		$1,067.6358	$1,067.64	$1,067.65	$1,067.50