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	$56.85	4.809%	$59.5839	$59.58	$59.60	$59.60
Purchase #2	$134.33	12.119%	$150.6095	$150.61	$150.60	$150.60
Purchase #3	$40.97	9.275%	$44.77	$44.77	$44.75	$44.80
Purchase #4	$82.32	4.282%	$85.8449	$85.84	$85.85	$85.80
Purchase #5	$160.35	12.406%	$180.243	$180.24	$180.25	$180.20
Purchase #6	$245.38	5.493%	$258.8587	$258.86	$258.85	$258.90
Purchase #7	$45.70	3.247%	$47.1839	$47.18	$47.20	$47.20
7 purchase totals =	$765.90		$827.0939	$827.08	$827.10	$827.10