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	$112.27	5.505%	$118.4505	$118.45	$118.45	$118.50
Purchase #2	$183.91	7.743%	$198.1502	$198.15	$198.15	$198.20
Purchase #3	$63.70	5.680%	$67.3182	$67.32	$67.30	$67.30
Purchase #4	$54.33	9.401%	$59.4376	$59.44	$59.45	$59.40
Purchase #5	$5.93	5.599%	$6.262	$6.26	$6.25	$6.30
Purchase #6	$177.82	3.377%	$183.825	$183.83	$183.85	$183.80
Purchase #7	$232.45	11.160%	$258.3914	$258.39	$258.40	$258.40
7 purchase totals =	$830.41		$891.8349	$891.84	$891.85	$891.90