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	$42.46	10.230%	$46.8037	$46.80	$46.80	$46.80
Purchase #2	$86.62	4.523%	$90.5378	$90.54	$90.55	$90.50
Purchase #3	$199.35	4.525%	$208.3706	$208.37	$208.35	$208.40
Purchase #4	$90.45	3.565%	$93.6745	$93.67	$93.65	$93.70
Purchase #5	$185.88	4.658%	$194.5383	$194.54	$194.55	$194.50
Purchase #6	$120.30	6.759%	$128.4311	$128.43	$128.45	$128.40
Purchase #7	$217.60	13.791%	$247.6092	$247.61	$247.60	$247.60
7 purchase totals =	$942.66		$1,009.9652	$1,009.96	$1,009.95	$1,009.90