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	$150.36	11.233%	$167.2499	$167.25	$167.25	$167.20
Purchase #2	$108.33	13.706%	$123.1777	$123.18	$123.20	$123.20
Purchase #3	$111.41	4.156%	$116.0402	$116.04	$116.05	$116.00
Purchase #4	$50.92	7.746%	$54.8643	$54.86	$54.85	$54.90
Purchase #5	$136.30	4.258%	$142.1037	$142.10	$142.10	$142.10
Purchase #6	$198.91	10.329%	$219.4554	$219.46	$219.45	$219.50
Purchase #7	$98.67	7.144%	$105.719	$105.72	$105.70	$105.70
7 purchase totals =	$854.90		$928.6102	$928.61	$928.60	$928.60