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	$90.65	8.766%	$98.5964	$98.60	$98.60	$98.60
Purchase #2	$108.42	10.587%	$119.8984	$119.90	$119.90	$119.90
Purchase #3	$155.59	5.609%	$164.317	$164.32	$164.30	$164.30
Purchase #4	$40.78	13.558%	$46.309	$46.31	$46.30	$46.30
Purchase #5	$147.36	13.696%	$167.5424	$167.54	$167.55	$167.50
Purchase #6	$248.69	8.337%	$269.4233	$269.42	$269.40	$269.40
Purchase #7	$194.83	7.187%	$208.8324	$208.83	$208.85	$208.80
7 purchase totals =	$986.32		$1,074.9189	$1,074.92	$1,074.90	$1,074.80