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	$111.61	10.543%	$123.377	$123.38	$123.40	$123.40
Purchase #2	$200.97	12.142%	$225.3718	$225.37	$225.35	$225.40
Purchase #3	$166.71	12.374%	$187.3387	$187.34	$187.35	$187.30
Purchase #4	$70.87	9.113%	$77.3284	$77.33	$77.35	$77.30
Purchase #5	$184.85	12.596%	$208.1337	$208.13	$208.15	$208.10
Purchase #6	$197.80	12.769%	$223.0571	$223.06	$223.05	$223.10
Purchase #7	$124.66	12.271%	$139.957	$139.96	$139.95	$140.00
7 purchase totals =	$1,057.47		$1,184.5637	$1,184.57	$1,184.60	$1,184.60