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	$196.66	4.498%	$205.5058	$205.51	$205.50	$205.50
Purchase #2	$227.73	9.609%	$249.6126	$249.61	$249.60	$249.60
Purchase #3	$37.73	10.339%	$41.6309	$41.63	$41.65	$41.60
Purchase #4	$28.89	11.819%	$32.3045	$32.30	$32.30	$32.30
Purchase #5	$69.64	12.108%	$78.072	$78.07	$78.05	$78.10
Purchase #6	$102.36	12.305%	$114.9554	$114.96	$114.95	$115.00
Purchase #7	$68.32	12.327%	$76.7418	$76.74	$76.75	$76.70
7 purchase totals =	$731.33		$798.8230	$798.82	$798.80	$798.80