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	$174.42	11.463%	$194.4138	$194.41	$194.40	$194.40
Purchase #2	$20.83	4.683%	$21.8055	$21.81	$21.80	$21.80
Purchase #3	$147.27	13.825%	$167.6301	$167.63	$167.65	$167.60
Purchase #4	$158.92	13.209%	$179.9117	$179.91	$179.90	$179.90
Purchase #5	$44.52	13.109%	$50.3561	$50.36	$50.35	$50.40
Purchase #6	$46.37	11.607%	$51.7522	$51.75	$51.75	$51.80
Purchase #7	$49.80	10.242%	$54.9005	$54.90	$54.90	$54.90
7 purchase totals =	$642.13		$720.7699	$720.77	$720.75	$720.80